diff --git a/codec.go b/codec.go
index 53be4c8d..13639ec3 100644
--- a/codec.go
+++ b/codec.go
@@ -16,11 +16,13 @@ limitations under the License.
 
 package galaxycache
 
+import "time"
+
 // Codec includes both the BinaryMarshaler and BinaryUnmarshaler
 // interfaces
 type Codec interface {
-	MarshalBinary() ([]byte, error)
-	UnmarshalBinary(data []byte) error
+	MarshalBinary() ([]byte, time.Time, error)
+	UnmarshalBinary(data []byte, expire time.Time) error
 }
 
 // Note: to ensure that unmarshaling is a read-only operation, bytes
@@ -32,48 +34,60 @@ func cloneBytes(b []byte) []byte {
 }
 
 // ByteCodec is a byte slice type that implements Codec
-type ByteCodec []byte
+type ByteCodec struct {
+	bytes  []byte
+	expire time.Time
+}
 
 // MarshalBinary on a ByteCodec returns the bytes
-func (c *ByteCodec) MarshalBinary() ([]byte, error) {
-	return *c, nil
+func (c *ByteCodec) MarshalBinary() ([]byte, time.Time, error) {
+	return c.bytes, c.expire, nil
 }
 
 // UnmarshalBinary on a ByteCodec sets the ByteCodec to
 // a copy of the provided data
-func (c *ByteCodec) UnmarshalBinary(data []byte) error {
-	*c = cloneBytes(data)
+func (c *ByteCodec) UnmarshalBinary(data []byte, expire time.Time) error {
+	c.bytes = cloneBytes(data)
+	c.expire = expire
 	return nil
 }
 
 // CopyingByteCodec is a byte slice type that implements Codec
 // and returns a copy of the bytes when marshaled
-type CopyingByteCodec []byte
+type CopyingByteCodec struct {
+	bytes  []byte
+	expire time.Time
+}
 
 // MarshalBinary on a CopyingByteCodec returns a copy of the bytes
-func (c *CopyingByteCodec) MarshalBinary() ([]byte, error) {
-	return cloneBytes(*c), nil
+func (c *CopyingByteCodec) MarshalBinary() ([]byte, time.Time, error) {
+	return cloneBytes(c.bytes), c.expire, nil
 }
 
 // UnmarshalBinary on a CopyingByteCodec sets the ByteCodec to
 // a copy of the provided data
-func (c *CopyingByteCodec) UnmarshalBinary(data []byte) error {
-	*c = cloneBytes(data)
+func (c *CopyingByteCodec) UnmarshalBinary(data []byte, expire time.Time) error {
+	c.bytes = cloneBytes(data)
+	c.expire = expire
 	return nil
 }
 
 // StringCodec is a string type that implements Codec
-type StringCodec string
+type StringCodec struct {
+	str    string
+	expire time.Time
+}
 
 // MarshalBinary on a StringCodec returns the bytes underlying
 // the string
-func (c *StringCodec) MarshalBinary() ([]byte, error) {
-	return []byte(*c), nil
+func (c *StringCodec) MarshalBinary() ([]byte, time.Time, error) {
+	return []byte(c.str), c.expire, nil
 }
 
 // UnmarshalBinary on a StringCodec sets the StringCodec to
 // a stringified copy of the provided data
-func (c *StringCodec) UnmarshalBinary(data []byte) error {
-	*c = StringCodec(data)
+func (c *StringCodec) UnmarshalBinary(data []byte, expire time.Time) error {
+	c.str = string(data)
+	c.expire = expire
 	return nil
 }
diff --git a/codec_test.go b/codec_test.go
index 76342233..0a4a9129 100644
--- a/codec_test.go
+++ b/codec_test.go
@@ -19,6 +19,7 @@ package galaxycache
 import (
 	"bytes"
 	"testing"
+	"time"
 )
 
 const testBytes = "some bytes"
@@ -51,25 +52,31 @@ func TestCodec(t *testing.T) {
 	for _, tc := range testCases {
 		t.Run(tc.testName, func(t *testing.T) {
 			inBytes := []byte(testBytes)
-			tc.codec.UnmarshalBinary(inBytes)
+			tc.codec.UnmarshalBinary(inBytes, time.Time{})
 			inBytes[0] = 'a' // change the original byte slice to ensure copy was made
-			marshaledBytes, err := tc.codec.MarshalBinary()
+			marshaledBytes, expTm, err := tc.codec.MarshalBinary()
 			if err != nil {
 				t.Errorf("Error marshaling from byteCodec: %s", err)
 			}
+			if !expTm.Equal(time.Time{}) {
+				t.Errorf("Expected empty expiration time")
+			}
 			if string(marshaledBytes) != testBytes {
 				t.Errorf("Unmarshal/Marshal resulted in %q; want %q", marshaledBytes, testBytes)
 			}
 
 			if tc.checkCopy {
 				marshaledBytes[0] = 'a' // change marshaled bytes to ensure full copy on marshal
-				secondMarshaledBytes, errM := tc.codec.MarshalBinary()
+				secondMarshaledBytes, expTm, errM := tc.codec.MarshalBinary()
 				if errM != nil {
 					t.Errorf("Error marshaling from byteCodec: %s", errM)
 				}
 				if bytes.Equal(marshaledBytes, secondMarshaledBytes) {
 					t.Errorf("Marshaling did not copy the bytes")
 				}
+				if !expTm.Equal(time.Time{}) {
+					t.Errorf("Expected empty expiration time")
+				}
 			}
 		})
 	}
diff --git a/galaxycache.go b/galaxycache.go
index 626db13d..e23a915f 100644
--- a/galaxycache.go
+++ b/galaxycache.go
@@ -436,7 +436,7 @@ func (g *Galaxy) Get(ctx context.Context, key string, dest Codec) error {
 		value.stats.touch()
 		g.recordRequest(ctx, hlvl, false)
 		g.recordStats(ctx, nil, MValueLength.M(int64(len(value.data))))
-		return dest.UnmarshalBinary(value.data)
+		return dest.UnmarshalBinary(value.data, value.expire)
 	}
 
 	span.Annotatef([]trace.Attribute{trace.BoolAttribute("cache_hit", false)}, "Cache miss")
@@ -456,7 +456,7 @@ func (g *Galaxy) Get(ctx context.Context, key string, dest Codec) error {
 	if destPopulated {
 		return nil
 	}
-	return dest.UnmarshalBinary(value.data)
+	return dest.UnmarshalBinary(value.data, value.expire)
 }
 
 type valWithLevel struct {
@@ -525,7 +525,7 @@ func (g *Galaxy) load(ctx context.Context, key string, dest Codec) (value *valWi
 			// probably boring (normal task movement), so not
 			// worth logging I imagine.
 		}
-		data, err := g.getLocally(ctx, key, dest)
+		data, expTm, err := g.getLocally(ctx, key, dest)
 		if err != nil {
 			g.Stats.BackendLoadErrors.Add(1)
 			g.recordStats(ctx, nil, MBackendLoadErrors.M(1))
@@ -535,7 +535,7 @@ func (g *Galaxy) load(ctx context.Context, key string, dest Codec) (value *valWi
 		g.Stats.CoalescedBackendLoads.Add(1)
 		g.recordStats(ctx, nil, MCoalescedBackendLoads.M(1))
 		destPopulated = true // only one caller of load gets this return value
-		value = newValWithStat(data, nil)
+		value = newValWithStat(data, nil, expTm)
 		g.populateCache(ctx, key, value, &g.mainCache)
 		return &valWithLevel{value, hitBackend, authoritative, peerErr, err}, nil
 	})
@@ -548,22 +548,22 @@ func (g *Galaxy) load(ctx context.Context, key string, dest Codec) (value *valWi
 	return
 }
 
-func (g *Galaxy) getLocally(ctx context.Context, key string, dest Codec) ([]byte, error) {
+func (g *Galaxy) getLocally(ctx context.Context, key string, dest Codec) ([]byte, time.Time, error) {
 	err := g.getter.Get(ctx, key, dest)
 	if err != nil {
-		return nil, err
+		return nil, time.Time{}, err
 	}
 	return dest.MarshalBinary()
 }
 
 func (g *Galaxy) getFromPeer(ctx context.Context, peer RemoteFetcher, key string) (*valWithStat, error) {
-	data, err := peer.Fetch(ctx, g.name, key)
+	data, expire, err := peer.Fetch(ctx, g.name, key)
 	if err != nil {
 		return nil, err
 	}
 	vi, ok := g.candidateCache.get(key)
 	if !ok {
-		vi = g.addNewToCandidateCache(key)
+		vi = g.addNewToCandidateCache(key, expire)
 	}
 
 	g.maybeUpdateHotCacheStats() // will update if at least a second has passed since the last update
@@ -573,7 +573,7 @@ func (g *Galaxy) getFromPeer(ctx context.Context, peer RemoteFetcher, key string
 		KeyQPS:  kStats.val(),
 		HCStats: g.hcStatsWithTime.hcs,
 	}
-	value := newValWithStat(data, kStats)
+	value := newValWithStat(data, kStats, expire)
 	if g.opts.promoter.ShouldPromote(key, value.data, stats) {
 		g.populateCache(ctx, key, value, &g.hotCache)
 	}
@@ -692,8 +692,9 @@ func (c *cache) stats() CacheStats {
 }
 
 type valWithStat struct {
-	data  []byte
-	stats *keyStats
+	data   []byte
+	stats  *keyStats
+	expire time.Time
 }
 
 // sizeOfValWithStats returns the total size of the value in the hot/main
@@ -704,13 +705,13 @@ func (v *valWithStat) size() int64 {
 	return int64(unsafe.Sizeof(*v.stats)) + int64(len(v.data)) + int64(unsafe.Sizeof(v)) + int64(unsafe.Sizeof(*v))
 }
 
-func (c *cache) setLRUOnEvicted(f func(key string, kStats *keyStats)) {
+func (c *cache) setLRUOnEvicted(f func(key string, kStats *keyStats, ttl time.Time)) {
 	c.lru.OnEvicted = func(key lru.Key, value interface{}) {
 		val := value.(*valWithStat)
 		c.nbytes -= int64(len(key.(string))) + val.size()
 		c.nevict++
 		if f != nil {
-			f(key.(string), val.stats)
+			f(key.(string), val.stats, val.expire)
 		}
 	}
 }
@@ -718,7 +719,7 @@ func (c *cache) setLRUOnEvicted(f func(key string, kStats *keyStats)) {
 func (c *cache) add(key string, value *valWithStat) {
 	c.mu.Lock()
 	defer c.mu.Unlock()
-	c.lru.Add(key, value)
+	c.lru.Add(key, value, value.expire)
 	c.nbytes += int64(len(key)) + value.size()
 }
 
diff --git a/galaxycache_test.go b/galaxycache_test.go
index fac06279..fe67486e 100644
--- a/galaxycache_test.go
+++ b/galaxycache_test.go
@@ -54,7 +54,7 @@ func setupStringGalaxyTest(cacheFills *AtomicInt) (*Galaxy, context.Context, cha
 		}
 		cacheFills.Add(1)
 		str := "ECHO:" + key
-		return dest.UnmarshalBinary([]byte(str))
+		return dest.UnmarshalBinary([]byte(str), time.Now().Add(5*time.Minute))
 	}))
 	return stringGalaxy, ctx, stringc
 }
@@ -75,7 +75,13 @@ func TestGetDupSuppress(t *testing.T) {
 				resc <- "ERROR:" + err.Error()
 				return
 			}
-			resc <- string(s)
+
+			ret, _, err := s.MarshalBinary()
+			if err != nil {
+				resc <- "ERROR MARSHAL: " + err.Error()
+				return
+			}
+			resc <- string(ret)
 		}()
 	}
 
@@ -150,7 +156,12 @@ func TestCacheEviction(t *testing.T) {
 		var res StringCodec
 		key := fmt.Sprintf("dummy-key-%d", bytesFlooded)
 		stringGalaxy.Get(ctx, key, &res)
-		bytesFlooded += int64(len(key) + len(res))
+
+		ret, _, err := res.MarshalBinary()
+		if err != nil {
+			t.Fatalf("marshaling binary: %v", err.Error())
+		}
+		bytesFlooded += int64(len(key) + len(ret))
 	}
 	evicts := stringGalaxy.mainCache.nevict - evict0
 	if evicts <= 0 {
@@ -179,12 +190,12 @@ func (fetcher *TestFetcher) Close() error {
 
 type testFetchers []RemoteFetcher
 
-func (fetcher *TestFetcher) Fetch(ctx context.Context, galaxy string, key string) ([]byte, error) {
+func (fetcher *TestFetcher) Fetch(ctx context.Context, galaxy string, key string) ([]byte, time.Time, error) {
 	if fetcher.fail {
-		return nil, errors.New("simulated error from peer")
+		return nil, time.Time{}, errors.New("simulated error from peer")
 	}
 	fetcher.hits++
-	return []byte("got:" + key), nil
+	return []byte("got:" + key), time.Time{}, nil
 }
 
 func (proto *TestProtocol) NewFetcher(url string) (RemoteFetcher, error) {
@@ -271,7 +282,7 @@ func TestPeers(t *testing.T) {
 			getter := func(_ context.Context, key string, dest Codec) error {
 				// these are local hits
 				testproto.TestFetchers["fetcher0"].hits++
-				return dest.UnmarshalBinary([]byte("got:" + key))
+				return dest.UnmarshalBinary([]byte("got:"+key), time.Now().Add(5*time.Minute))
 			}
 
 			testGalaxy := universe.NewGalaxy("TestPeers-galaxy", tc.cacheSize, GetterFunc(getter), WithPromoter(&promoter.ProbabilisticPromoter{ProbDenominator: 10}))
@@ -293,8 +304,14 @@ func TestPeers(t *testing.T) {
 					t.Errorf("%s: error on key %q: %v", tc.testName, key, err)
 					continue
 				}
-				if string(got) != want {
-					t.Errorf("%s: for key %q, got %q; want %q", tc.testName, key, got, want)
+
+				ret, _, err := got.MarshalBinary()
+				if err != nil {
+					t.Errorf("%s: error marshaling on key %q: %v", tc.testName, key, err)
+					continue
+				}
+				if string(ret) != want {
+					t.Errorf("%s: for key %q, got %q; want %q", tc.testName, key, ret, want)
 				}
 			}
 			for name, fetcher := range testproto.TestFetchers {
@@ -335,7 +352,7 @@ func TestNoDedup(t *testing.T) {
 	const testkey = "testkey"
 	const testval = "testval"
 	g := universe.NewGalaxy("testgalaxy", 1024, GetterFunc(func(_ context.Context, key string, dest Codec) error {
-		return dest.UnmarshalBinary([]byte(testval))
+		return dest.UnmarshalBinary([]byte(testval), time.Now().Add(5*time.Minute))
 	}))
 
 	orderedGroup := &orderedFlightGroup{
@@ -359,7 +376,13 @@ func TestNoDedup(t *testing.T) {
 				resc <- "ERROR:" + err.Error()
 				return
 			}
-			resc <- string(s)
+
+			ret, _, err := s.MarshalBinary()
+			if err != nil {
+				resc <- "ERROR MARSHAL:" + err.Error()
+				return
+			}
+			resc <- string(ret)
 		}()
 	}
 
@@ -386,7 +409,7 @@ func TestNoDedup(t *testing.T) {
 	// upon entry, we would increment nbytes twice but the entry would
 	// only be in the cache once.
 	testKStats := keyStats{dQPS: dampedQPS{period: time.Second}}
-	testvws := newValWithStat([]byte(testval), &testKStats)
+	testvws := newValWithStat([]byte(testval), &testKStats, time.Now().Add(1*time.Second))
 	wantBytes := int64(len(testkey)) + testvws.size()
 	if g.mainCache.nbytes != wantBytes {
 		t.Errorf("cache has %d bytes, want %d", g.mainCache.nbytes, wantBytes)
@@ -454,14 +477,14 @@ func TestHotcache(t *testing.T) {
 		t.Run(tc.name, func(t *testing.T) {
 			u := NewUniverse(&TestProtocol{}, "test-universe")
 			g := u.NewGalaxy("test-galaxy", 1<<20, GetterFunc(func(_ context.Context, key string, dest Codec) error {
-				return dest.UnmarshalBinary([]byte("hello"))
+				return dest.UnmarshalBinary([]byte("hello"), time.Now().Add(5*time.Minute))
 			}))
 			kStats := &keyStats{
 				dQPS: dampedQPS{
 					period: time.Second,
 				},
 			}
-			value := newValWithStat([]byte("hello"), kStats)
+			value := newValWithStat([]byte("hello"), kStats, time.Now().Add(1*time.Second))
 			g.hotCache.add(keyToAdd, value)
 			now := time.Now()
 			// blast the key in the hotcache with a bunch of hypothetical gets every few seconds
@@ -476,7 +499,7 @@ func TestHotcache(t *testing.T) {
 			if math.Abs(val-tc.expectedBurstQPS) > val/100 { // ensure less than %1 error
 				t.Errorf("QPS after bursts: %f, Wanted: %f", val, tc.expectedBurstQPS)
 			}
-			value2 := newValWithStat([]byte("hello there"), nil)
+			value2 := newValWithStat([]byte("hello there"), nil, time.Now().Add(1*time.Second))
 
 			g.hotCache.add(keyToAdd+"2", value2) // ensure that hcStats are properly updated after adding
 			g.maybeUpdateHotCacheStats()
@@ -568,7 +591,7 @@ func TestPromotion(t *testing.T) {
 			fetcher := &TestFetcher{}
 			testProto := &TestProtocol{}
 			getter := func(_ context.Context, key string, dest Codec) error {
-				return dest.UnmarshalBinary([]byte("got:" + key))
+				return dest.UnmarshalBinary([]byte("got:"+key), time.Now().Add(5*time.Minute))
 			}
 			universe := NewUniverse(testProto, "promotion-test")
 			galaxy := universe.NewGalaxy("test-galaxy", tc.cacheSize, GetterFunc(getter), WithPromoter(tc.promoter))
@@ -594,7 +617,7 @@ func TestRecorder(t *testing.T) {
 	meter.Register(testView)
 
 	getter := func(_ context.Context, key string, dest Codec) error {
-		return dest.UnmarshalBinary([]byte("got:" + key))
+		return dest.UnmarshalBinary([]byte("got:"+key), time.Now().Add(5*time.Minute))
 	}
 	u := NewUniverse(&TestProtocol{}, "test-universe", WithRecorder(meter))
 	g := u.NewGalaxy("test", 1024, GetterFunc(getter))
diff --git a/galaxycachepb/galaxycache.pb.go b/galaxycachepb/galaxycache.pb.go
index 116e3d79..401ed086 100644
--- a/galaxycachepb/galaxycache.pb.go
+++ b/galaxycachepb/galaxycache.pb.go
@@ -1,212 +1,256 @@
+//
+//Copyright 2012 Google Inc.
+//
+//Licensed under the Apache License, Version 2.0 (the "License");
+//you may not use this file except in compliance with the License.
+//You may obtain a copy of the License at
+//
+//http://www.apache.org/licenses/LICENSE-2.0
+//
+//Unless required by applicable law or agreed to in writing, software
+//distributed under the License is distributed on an "AS IS" BASIS,
+//WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+//See the License for the specific language governing permissions and
+//limitations under the License.
+
 // Code generated by protoc-gen-go. DO NOT EDIT.
+// versions:
+// 	protoc-gen-go v1.27.1
+// 	protoc        v3.19.1
 // source: galaxycache.proto
 
 package galaxycachepb
 
 import (
-	context "context"
-	fmt "fmt"
-	proto "github.com/golang/protobuf/proto"
-	grpc "google.golang.org/grpc"
-	math "math"
+	protoreflect "google.golang.org/protobuf/reflect/protoreflect"
+	protoimpl "google.golang.org/protobuf/runtime/protoimpl"
+	reflect "reflect"
+	sync "sync"
 )
 
-// Reference imports to suppress errors if they are not otherwise used.
-var _ = proto.Marshal
-var _ = fmt.Errorf
-var _ = math.Inf
-
-// This is a compile-time assertion to ensure that this generated file
-// is compatible with the proto package it is being compiled against.
-// A compilation error at this line likely means your copy of the
-// proto package needs to be updated.
-const _ = proto.ProtoPackageIsVersion3 // please upgrade the proto package
+const (
+	// Verify that this generated code is sufficiently up-to-date.
+	_ = protoimpl.EnforceVersion(20 - protoimpl.MinVersion)
+	// Verify that runtime/protoimpl is sufficiently up-to-date.
+	_ = protoimpl.EnforceVersion(protoimpl.MaxVersion - 20)
+)
 
 type GetRequest struct {
-	Galaxy               string   `protobuf:"bytes,1,opt,name=galaxy,proto3" json:"galaxy,omitempty"`
-	Key                  string   `protobuf:"bytes,2,opt,name=key,proto3" json:"key,omitempty"`
-	XXX_NoUnkeyedLiteral struct{} `json:"-"`
-	XXX_unrecognized     []byte   `json:"-"`
-	XXX_sizecache        int32    `json:"-"`
-}
+	state         protoimpl.MessageState
+	sizeCache     protoimpl.SizeCache
+	unknownFields protoimpl.UnknownFields
 
-func (m *GetRequest) Reset()         { *m = GetRequest{} }
-func (m *GetRequest) String() string { return proto.CompactTextString(m) }
-func (*GetRequest) ProtoMessage()    {}
-func (*GetRequest) Descriptor() ([]byte, []int) {
-	return fileDescriptor_23bd509ca7b74957, []int{0}
+	Galaxy string `protobuf:"bytes,1,opt,name=galaxy,proto3" json:"galaxy,omitempty"`
+	Key    string `protobuf:"bytes,2,opt,name=key,proto3" json:"key,omitempty"` // not actually required/guaranteed to be UTF-8
 }
 
-func (m *GetRequest) XXX_Unmarshal(b []byte) error {
-	return xxx_messageInfo_GetRequest.Unmarshal(m, b)
-}
-func (m *GetRequest) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
-	return xxx_messageInfo_GetRequest.Marshal(b, m, deterministic)
-}
-func (m *GetRequest) XXX_Merge(src proto.Message) {
-	xxx_messageInfo_GetRequest.Merge(m, src)
+func (x *GetRequest) Reset() {
+	*x = GetRequest{}
+	if protoimpl.UnsafeEnabled {
+		mi := &file_galaxycache_proto_msgTypes[0]
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		ms.StoreMessageInfo(mi)
+	}
 }
-func (m *GetRequest) XXX_Size() int {
-	return xxx_messageInfo_GetRequest.Size(m)
+
+func (x *GetRequest) String() string {
+	return protoimpl.X.MessageStringOf(x)
 }
-func (m *GetRequest) XXX_DiscardUnknown() {
-	xxx_messageInfo_GetRequest.DiscardUnknown(m)
+
+func (*GetRequest) ProtoMessage() {}
+
+func (x *GetRequest) ProtoReflect() protoreflect.Message {
+	mi := &file_galaxycache_proto_msgTypes[0]
+	if protoimpl.UnsafeEnabled && x != nil {
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		if ms.LoadMessageInfo() == nil {
+			ms.StoreMessageInfo(mi)
+		}
+		return ms
+	}
+	return mi.MessageOf(x)
 }
 
-var xxx_messageInfo_GetRequest proto.InternalMessageInfo
+// Deprecated: Use GetRequest.ProtoReflect.Descriptor instead.
+func (*GetRequest) Descriptor() ([]byte, []int) {
+	return file_galaxycache_proto_rawDescGZIP(), []int{0}
+}
 
-func (m *GetRequest) GetGalaxy() string {
-	if m != nil {
-		return m.Galaxy
+func (x *GetRequest) GetGalaxy() string {
+	if x != nil {
+		return x.Galaxy
 	}
 	return ""
 }
 
-func (m *GetRequest) GetKey() string {
-	if m != nil {
-		return m.Key
+func (x *GetRequest) GetKey() string {
+	if x != nil {
+		return x.Key
 	}
 	return ""
 }
 
 type GetResponse struct {
-	Value                []byte   `protobuf:"bytes,1,opt,name=value,proto3" json:"value,omitempty"`
-	MinuteQps            float64  `protobuf:"fixed64,2,opt,name=minute_qps,json=minuteQps,proto3" json:"minute_qps,omitempty"`
-	XXX_NoUnkeyedLiteral struct{} `json:"-"`
-	XXX_unrecognized     []byte   `json:"-"`
-	XXX_sizecache        int32    `json:"-"`
-}
+	state         protoimpl.MessageState
+	sizeCache     protoimpl.SizeCache
+	unknownFields protoimpl.UnknownFields
 
-func (m *GetResponse) Reset()         { *m = GetResponse{} }
-func (m *GetResponse) String() string { return proto.CompactTextString(m) }
-func (*GetResponse) ProtoMessage()    {}
-func (*GetResponse) Descriptor() ([]byte, []int) {
-	return fileDescriptor_23bd509ca7b74957, []int{1}
+	Value     []byte  `protobuf:"bytes,1,opt,name=value,proto3" json:"value,omitempty"`
+	MinuteQps float64 `protobuf:"fixed64,2,opt,name=minute_qps,json=minuteQps,proto3" json:"minute_qps,omitempty"`
+	Expire    int64   `protobuf:"varint,3,opt,name=expire,proto3" json:"expire,omitempty"`
 }
 
-func (m *GetResponse) XXX_Unmarshal(b []byte) error {
-	return xxx_messageInfo_GetResponse.Unmarshal(m, b)
-}
-func (m *GetResponse) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
-	return xxx_messageInfo_GetResponse.Marshal(b, m, deterministic)
-}
-func (m *GetResponse) XXX_Merge(src proto.Message) {
-	xxx_messageInfo_GetResponse.Merge(m, src)
+func (x *GetResponse) Reset() {
+	*x = GetResponse{}
+	if protoimpl.UnsafeEnabled {
+		mi := &file_galaxycache_proto_msgTypes[1]
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		ms.StoreMessageInfo(mi)
+	}
 }
-func (m *GetResponse) XXX_Size() int {
-	return xxx_messageInfo_GetResponse.Size(m)
+
+func (x *GetResponse) String() string {
+	return protoimpl.X.MessageStringOf(x)
 }
-func (m *GetResponse) XXX_DiscardUnknown() {
-	xxx_messageInfo_GetResponse.DiscardUnknown(m)
+
+func (*GetResponse) ProtoMessage() {}
+
+func (x *GetResponse) ProtoReflect() protoreflect.Message {
+	mi := &file_galaxycache_proto_msgTypes[1]
+	if protoimpl.UnsafeEnabled && x != nil {
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		if ms.LoadMessageInfo() == nil {
+			ms.StoreMessageInfo(mi)
+		}
+		return ms
+	}
+	return mi.MessageOf(x)
 }
 
-var xxx_messageInfo_GetResponse proto.InternalMessageInfo
+// Deprecated: Use GetResponse.ProtoReflect.Descriptor instead.
+func (*GetResponse) Descriptor() ([]byte, []int) {
+	return file_galaxycache_proto_rawDescGZIP(), []int{1}
+}
 
-func (m *GetResponse) GetValue() []byte {
-	if m != nil {
-		return m.Value
+func (x *GetResponse) GetValue() []byte {
+	if x != nil {
+		return x.Value
 	}
 	return nil
 }
 
-func (m *GetResponse) GetMinuteQps() float64 {
-	if m != nil {
-		return m.MinuteQps
+func (x *GetResponse) GetMinuteQps() float64 {
+	if x != nil {
+		return x.MinuteQps
 	}
 	return 0
 }
 
-func init() {
-	proto.RegisterType((*GetRequest)(nil), "galaxycachepb.GetRequest")
-	proto.RegisterType((*GetResponse)(nil), "galaxycachepb.GetResponse")
+func (x *GetResponse) GetExpire() int64 {
+	if x != nil {
+		return x.Expire
+	}
+	return 0
 }
 
-func init() { proto.RegisterFile("galaxycache.proto", fileDescriptor_23bd509ca7b74957) }
+var File_galaxycache_proto protoreflect.FileDescriptor
 
-var fileDescriptor_23bd509ca7b74957 = []byte{
-	// 186 bytes of a gzipped FileDescriptorProto
-	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0xff, 0xe2, 0x12, 0x4c, 0x4f, 0xcc, 0x49,
-	0xac, 0xa8, 0x4c, 0x4e, 0x4c, 0xce, 0x48, 0xd5, 0x2b, 0x28, 0xca, 0x2f, 0xc9, 0x17, 0xe2, 0x45,
-	0x12, 0x2a, 0x48, 0x52, 0x32, 0xe3, 0xe2, 0x72, 0x4f, 0x2d, 0x09, 0x4a, 0x2d, 0x2c, 0x4d, 0x2d,
-	0x2e, 0x11, 0x12, 0xe3, 0x62, 0x83, 0x48, 0x4b, 0x30, 0x2a, 0x30, 0x6a, 0x70, 0x06, 0x41, 0x79,
-	0x42, 0x02, 0x5c, 0xcc, 0xd9, 0xa9, 0x95, 0x12, 0x4c, 0x60, 0x41, 0x10, 0x53, 0xc9, 0x89, 0x8b,
-	0x1b, 0xac, 0xaf, 0xb8, 0x20, 0x3f, 0xaf, 0x38, 0x55, 0x48, 0x84, 0x8b, 0xb5, 0x2c, 0x31, 0xa7,
-	0x34, 0x15, 0xac, 0x8f, 0x27, 0x08, 0xc2, 0x11, 0x92, 0xe5, 0xe2, 0xca, 0xcd, 0xcc, 0x2b, 0x2d,
-	0x49, 0x8d, 0x2f, 0x2c, 0x28, 0x06, 0xeb, 0x66, 0x0c, 0xe2, 0x84, 0x88, 0x04, 0x16, 0x14, 0x1b,
-	0x85, 0x72, 0x71, 0xbb, 0x83, 0xcd, 0x77, 0x06, 0x39, 0x46, 0xc8, 0x0d, 0x6c, 0xa4, 0x5b, 0x51,
-	0x7e, 0x6e, 0x40, 0x6a, 0x6a, 0x91, 0x90, 0xa4, 0x1e, 0x8a, 0x4b, 0xf5, 0x10, 0xce, 0x94, 0x92,
-	0xc2, 0x26, 0x05, 0x71, 0x89, 0x12, 0x43, 0x12, 0x1b, 0xd8, 0xa3, 0xc6, 0x80, 0x00, 0x00, 0x00,
-	0xff, 0xff, 0x84, 0x48, 0x7a, 0xc8, 0xfd, 0x00, 0x00, 0x00,
+var file_galaxycache_proto_rawDesc = []byte{
+	0x0a, 0x11, 0x67, 0x61, 0x6c, 0x61, 0x78, 0x79, 0x63, 0x61, 0x63, 0x68, 0x65, 0x2e, 0x70, 0x72,
+	0x6f, 0x74, 0x6f, 0x12, 0x0d, 0x67, 0x61, 0x6c, 0x61, 0x78, 0x79, 0x63, 0x61, 0x63, 0x68, 0x65,
+	0x70, 0x62, 0x22, 0x36, 0x0a, 0x0a, 0x47, 0x65, 0x74, 0x52, 0x65, 0x71, 0x75, 0x65, 0x73, 0x74,
+	0x12, 0x16, 0x0a, 0x06, 0x67, 0x61, 0x6c, 0x61, 0x78, 0x79, 0x18, 0x01, 0x20, 0x01, 0x28, 0x09,
+	0x52, 0x06, 0x67, 0x61, 0x6c, 0x61, 0x78, 0x79, 0x12, 0x10, 0x0a, 0x03, 0x6b, 0x65, 0x79, 0x18,
+	0x02, 0x20, 0x01, 0x28, 0x09, 0x52, 0x03, 0x6b, 0x65, 0x79, 0x22, 0x5a, 0x0a, 0x0b, 0x47, 0x65,
+	0x74, 0x52, 0x65, 0x73, 0x70, 0x6f, 0x6e, 0x73, 0x65, 0x12, 0x14, 0x0a, 0x05, 0x76, 0x61, 0x6c,
+	0x75, 0x65, 0x18, 0x01, 0x20, 0x01, 0x28, 0x0c, 0x52, 0x05, 0x76, 0x61, 0x6c, 0x75, 0x65, 0x12,
+	0x1d, 0x0a, 0x0a, 0x6d, 0x69, 0x6e, 0x75, 0x74, 0x65, 0x5f, 0x71, 0x70, 0x73, 0x18, 0x02, 0x20,
+	0x01, 0x28, 0x01, 0x52, 0x09, 0x6d, 0x69, 0x6e, 0x75, 0x74, 0x65, 0x51, 0x70, 0x73, 0x12, 0x16,
+	0x0a, 0x06, 0x65, 0x78, 0x70, 0x69, 0x72, 0x65, 0x18, 0x03, 0x20, 0x01, 0x28, 0x03, 0x52, 0x06,
+	0x65, 0x78, 0x70, 0x69, 0x72, 0x65, 0x32, 0x55, 0x0a, 0x0b, 0x47, 0x61, 0x6c, 0x61, 0x78, 0x79,
+	0x43, 0x61, 0x63, 0x68, 0x65, 0x12, 0x46, 0x0a, 0x0b, 0x47, 0x65, 0x74, 0x46, 0x72, 0x6f, 0x6d,
+	0x50, 0x65, 0x65, 0x72, 0x12, 0x19, 0x2e, 0x67, 0x61, 0x6c, 0x61, 0x78, 0x79, 0x63, 0x61, 0x63,
+	0x68, 0x65, 0x70, 0x62, 0x2e, 0x47, 0x65, 0x74, 0x52, 0x65, 0x71, 0x75, 0x65, 0x73, 0x74, 0x1a,
+	0x1a, 0x2e, 0x67, 0x61, 0x6c, 0x61, 0x78, 0x79, 0x63, 0x61, 0x63, 0x68, 0x65, 0x70, 0x62, 0x2e,
+	0x47, 0x65, 0x74, 0x52, 0x65, 0x73, 0x70, 0x6f, 0x6e, 0x73, 0x65, 0x22, 0x00, 0x42, 0x11, 0x5a,
+	0x0f, 0x2e, 0x2f, 0x67, 0x61, 0x6c, 0x61, 0x78, 0x79, 0x63, 0x61, 0x63, 0x68, 0x65, 0x70, 0x62,
+	0x62, 0x06, 0x70, 0x72, 0x6f, 0x74, 0x6f, 0x33,
 }
 
-// Reference imports to suppress errors if they are not otherwise used.
-var _ context.Context
-var _ grpc.ClientConn
-
-// This is a compile-time assertion to ensure that this generated file
-// is compatible with the grpc package it is being compiled against.
-const _ = grpc.SupportPackageIsVersion4
-
-// GalaxyCacheClient is the client API for GalaxyCache service.
-//
-// For semantics around ctx use and closing/ending streaming RPCs, please refer to https://godoc.org/google.golang.org/grpc#ClientConn.NewStream.
-type GalaxyCacheClient interface {
-	GetFromPeer(ctx context.Context, in *GetRequest, opts ...grpc.CallOption) (*GetResponse, error)
-}
-
-type galaxyCacheClient struct {
-	cc *grpc.ClientConn
-}
+var (
+	file_galaxycache_proto_rawDescOnce sync.Once
+	file_galaxycache_proto_rawDescData = file_galaxycache_proto_rawDesc
+)
 
-func NewGalaxyCacheClient(cc *grpc.ClientConn) GalaxyCacheClient {
-	return &galaxyCacheClient{cc}
+func file_galaxycache_proto_rawDescGZIP() []byte {
+	file_galaxycache_proto_rawDescOnce.Do(func() {
+		file_galaxycache_proto_rawDescData = protoimpl.X.CompressGZIP(file_galaxycache_proto_rawDescData)
+	})
+	return file_galaxycache_proto_rawDescData
 }
 
-func (c *galaxyCacheClient) GetFromPeer(ctx context.Context, in *GetRequest, opts ...grpc.CallOption) (*GetResponse, error) {
-	out := new(GetResponse)
-	err := c.cc.Invoke(ctx, "/galaxycachepb.GalaxyCache/GetFromPeer", in, out, opts...)
-	if err != nil {
-		return nil, err
-	}
-	return out, nil
+var file_galaxycache_proto_msgTypes = make([]protoimpl.MessageInfo, 2)
+var file_galaxycache_proto_goTypes = []interface{}{
+	(*GetRequest)(nil),  // 0: galaxycachepb.GetRequest
+	(*GetResponse)(nil), // 1: galaxycachepb.GetResponse
 }
-
-// GalaxyCacheServer is the server API for GalaxyCache service.
-type GalaxyCacheServer interface {
-	GetFromPeer(context.Context, *GetRequest) (*GetResponse, error)
+var file_galaxycache_proto_depIdxs = []int32{
+	0, // 0: galaxycachepb.GalaxyCache.GetFromPeer:input_type -> galaxycachepb.GetRequest
+	1, // 1: galaxycachepb.GalaxyCache.GetFromPeer:output_type -> galaxycachepb.GetResponse
+	1, // [1:2] is the sub-list for method output_type
+	0, // [0:1] is the sub-list for method input_type
+	0, // [0:0] is the sub-list for extension type_name
+	0, // [0:0] is the sub-list for extension extendee
+	0, // [0:0] is the sub-list for field type_name
 }
 
-func RegisterGalaxyCacheServer(s *grpc.Server, srv GalaxyCacheServer) {
-	s.RegisterService(&_GalaxyCache_serviceDesc, srv)
-}
-
-func _GalaxyCache_GetFromPeer_Handler(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) {
-	in := new(GetRequest)
-	if err := dec(in); err != nil {
-		return nil, err
-	}
-	if interceptor == nil {
-		return srv.(GalaxyCacheServer).GetFromPeer(ctx, in)
-	}
-	info := &grpc.UnaryServerInfo{
-		Server:     srv,
-		FullMethod: "/galaxycachepb.GalaxyCache/GetFromPeer",
+func init() { file_galaxycache_proto_init() }
+func file_galaxycache_proto_init() {
+	if File_galaxycache_proto != nil {
+		return
 	}
-	handler := func(ctx context.Context, req interface{}) (interface{}, error) {
-		return srv.(GalaxyCacheServer).GetFromPeer(ctx, req.(*GetRequest))
+	if !protoimpl.UnsafeEnabled {
+		file_galaxycache_proto_msgTypes[0].Exporter = func(v interface{}, i int) interface{} {
+			switch v := v.(*GetRequest); i {
+			case 0:
+				return &v.state
+			case 1:
+				return &v.sizeCache
+			case 2:
+				return &v.unknownFields
+			default:
+				return nil
+			}
+		}
+		file_galaxycache_proto_msgTypes[1].Exporter = func(v interface{}, i int) interface{} {
+			switch v := v.(*GetResponse); i {
+			case 0:
+				return &v.state
+			case 1:
+				return &v.sizeCache
+			case 2:
+				return &v.unknownFields
+			default:
+				return nil
+			}
+		}
 	}
-	return interceptor(ctx, in, info, handler)
-}
-
-var _GalaxyCache_serviceDesc = grpc.ServiceDesc{
-	ServiceName: "galaxycachepb.GalaxyCache",
-	HandlerType: (*GalaxyCacheServer)(nil),
-	Methods: []grpc.MethodDesc{
-		{
-			MethodName: "GetFromPeer",
-			Handler:    _GalaxyCache_GetFromPeer_Handler,
+	type x struct{}
+	out := protoimpl.TypeBuilder{
+		File: protoimpl.DescBuilder{
+			GoPackagePath: reflect.TypeOf(x{}).PkgPath(),
+			RawDescriptor: file_galaxycache_proto_rawDesc,
+			NumEnums:      0,
+			NumMessages:   2,
+			NumExtensions: 0,
+			NumServices:   1,
 		},
-	},
-	Streams:  []grpc.StreamDesc{},
-	Metadata: "galaxycache.proto",
+		GoTypes:           file_galaxycache_proto_goTypes,
+		DependencyIndexes: file_galaxycache_proto_depIdxs,
+		MessageInfos:      file_galaxycache_proto_msgTypes,
+	}.Build()
+	File_galaxycache_proto = out.File
+	file_galaxycache_proto_rawDesc = nil
+	file_galaxycache_proto_goTypes = nil
+	file_galaxycache_proto_depIdxs = nil
 }
diff --git a/galaxycachepb/galaxycache.proto b/galaxycachepb/galaxycache.proto
index a30fb340..00fdfc23 100644
--- a/galaxycachepb/galaxycache.proto
+++ b/galaxycachepb/galaxycache.proto
@@ -17,6 +17,8 @@ limitations under the License.
 syntax = "proto3";
 
 package galaxycachepb;
+option go_package = "./galaxycachepb";
+
 
 message GetRequest {
   string galaxy = 1;
@@ -26,8 +28,9 @@ message GetRequest {
 message GetResponse {
   bytes value = 1;
   double minute_qps = 2;
+  int64 expire = 3;
 }
 
 service GalaxyCache {
   rpc GetFromPeer(GetRequest) returns (GetResponse) {}
-}
\ No newline at end of file
+}
diff --git a/galaxycachepb/galaxycache_grpc.pb.go b/galaxycachepb/galaxycache_grpc.pb.go
new file mode 100644
index 00000000..3719ccef
--- /dev/null
+++ b/galaxycachepb/galaxycache_grpc.pb.go
@@ -0,0 +1,101 @@
+// Code generated by protoc-gen-go-grpc. DO NOT EDIT.
+
+package galaxycachepb
+
+import (
+	context "context"
+	grpc "google.golang.org/grpc"
+	codes "google.golang.org/grpc/codes"
+	status "google.golang.org/grpc/status"
+)
+
+// This is a compile-time assertion to ensure that this generated file
+// is compatible with the grpc package it is being compiled against.
+// Requires gRPC-Go v1.32.0 or later.
+const _ = grpc.SupportPackageIsVersion7
+
+// GalaxyCacheClient is the client API for GalaxyCache service.
+//
+// For semantics around ctx use and closing/ending streaming RPCs, please refer to https://pkg.go.dev/google.golang.org/grpc/?tab=doc#ClientConn.NewStream.
+type GalaxyCacheClient interface {
+	GetFromPeer(ctx context.Context, in *GetRequest, opts ...grpc.CallOption) (*GetResponse, error)
+}
+
+type galaxyCacheClient struct {
+	cc grpc.ClientConnInterface
+}
+
+func NewGalaxyCacheClient(cc grpc.ClientConnInterface) GalaxyCacheClient {
+	return &galaxyCacheClient{cc}
+}
+
+func (c *galaxyCacheClient) GetFromPeer(ctx context.Context, in *GetRequest, opts ...grpc.CallOption) (*GetResponse, error) {
+	out := new(GetResponse)
+	err := c.cc.Invoke(ctx, "/galaxycachepb.GalaxyCache/GetFromPeer", in, out, opts...)
+	if err != nil {
+		return nil, err
+	}
+	return out, nil
+}
+
+// GalaxyCacheServer is the server API for GalaxyCache service.
+// All implementations must embed UnimplementedGalaxyCacheServer
+// for forward compatibility
+type GalaxyCacheServer interface {
+	GetFromPeer(context.Context, *GetRequest) (*GetResponse, error)
+	mustEmbedUnimplementedGalaxyCacheServer()
+}
+
+// UnimplementedGalaxyCacheServer must be embedded to have forward compatible implementations.
+type UnimplementedGalaxyCacheServer struct {
+}
+
+func (UnimplementedGalaxyCacheServer) GetFromPeer(context.Context, *GetRequest) (*GetResponse, error) {
+	return nil, status.Errorf(codes.Unimplemented, "method GetFromPeer not implemented")
+}
+func (UnimplementedGalaxyCacheServer) mustEmbedUnimplementedGalaxyCacheServer() {}
+
+// UnsafeGalaxyCacheServer may be embedded to opt out of forward compatibility for this service.
+// Use of this interface is not recommended, as added methods to GalaxyCacheServer will
+// result in compilation errors.
+type UnsafeGalaxyCacheServer interface {
+	mustEmbedUnimplementedGalaxyCacheServer()
+}
+
+func RegisterGalaxyCacheServer(s grpc.ServiceRegistrar, srv GalaxyCacheServer) {
+	s.RegisterService(&GalaxyCache_ServiceDesc, srv)
+}
+
+func _GalaxyCache_GetFromPeer_Handler(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) {
+	in := new(GetRequest)
+	if err := dec(in); err != nil {
+		return nil, err
+	}
+	if interceptor == nil {
+		return srv.(GalaxyCacheServer).GetFromPeer(ctx, in)
+	}
+	info := &grpc.UnaryServerInfo{
+		Server:     srv,
+		FullMethod: "/galaxycachepb.GalaxyCache/GetFromPeer",
+	}
+	handler := func(ctx context.Context, req interface{}) (interface{}, error) {
+		return srv.(GalaxyCacheServer).GetFromPeer(ctx, req.(*GetRequest))
+	}
+	return interceptor(ctx, in, info, handler)
+}
+
+// GalaxyCache_ServiceDesc is the grpc.ServiceDesc for GalaxyCache service.
+// It's only intended for direct use with grpc.RegisterService,
+// and not to be introspected or modified (even as a copy)
+var GalaxyCache_ServiceDesc = grpc.ServiceDesc{
+	ServiceName: "galaxycachepb.GalaxyCache",
+	HandlerType: (*GalaxyCacheServer)(nil),
+	Methods: []grpc.MethodDesc{
+		{
+			MethodName: "GetFromPeer",
+			Handler:    _GalaxyCache_GetFromPeer_Handler,
+		},
+	},
+	Streams:  []grpc.StreamDesc{},
+	Metadata: "galaxycache.proto",
+}
diff --git a/go.mod b/go.mod
index 12af9092..75fb9276 100644
--- a/go.mod
+++ b/go.mod
@@ -7,4 +7,5 @@ require (
 	go.opencensus.io v0.22.5
 	golang.org/x/net v0.0.0-20210119194325-5f4716e94777 // indirect
 	google.golang.org/grpc v1.35.0
+	google.golang.org/protobuf v1.25.0
 )
diff --git a/go.sum b/go.sum
index 8f329b03..97d8b4f6 100644
--- a/go.sum
+++ b/go.sum
@@ -8,13 +8,13 @@ github.com/envoyproxy/go-control-plane v0.9.0/go.mod h1:YTl/9mNaCwkRvm6d1a2C3ymF
 github.com/envoyproxy/go-control-plane v0.9.1-0.20191026205805-5f8ba28d4473/go.mod h1:YTl/9mNaCwkRvm6d1a2C3ymFceY/DCBVvsKhRF0iEA4=
 github.com/envoyproxy/go-control-plane v0.9.9-0.20201210154907-fd9021fe5dad/go.mod h1:cXg6YxExXjJnVBQHBLXeUAgxn2UodCpnH306RInaBQk=
 github.com/envoyproxy/protoc-gen-validate v0.1.0/go.mod h1:iSmxcyjqTsJpI2R4NaDN7+kN2VEUnK/pcBlmesArF7c=
-github.com/golang/glog v0.0.0-20160126235308-23def4e6c14b h1:VKtxabqXZkF25pY9ekfRL6a582T4P37/31XEstQ5p58=
+github.com/gogo/protobuf v1.3.2 h1:Ov1cvc58UF3b5XjBnZv7+opcTcQFZebYjWzi34vdm4Q=
+github.com/gogo/protobuf v1.3.2/go.mod h1:P1XiOD3dCwIKUDQYPy72D8LYyHL2YPYrpS2s69NZV8Q=
 github.com/golang/glog v0.0.0-20160126235308-23def4e6c14b/go.mod h1:SBH7ygxi8pfUlaOkMMuAQtPIUF8ecWP5IEl/CR7VP2Q=
 github.com/golang/groupcache v0.0.0-20190702054246-869f871628b6 h1:ZgQEtGgCBiWRM39fZuwSd1LwSqqSW0hOdXCYYDX0R3I=
 github.com/golang/groupcache v0.0.0-20190702054246-869f871628b6/go.mod h1:cIg4eruTrX1D+g88fzRXU5OdNfaM+9IcxsU14FzY7Hc=
 github.com/golang/mock v1.1.1/go.mod h1:oTYuIxOrZwtPieC+H1uAHpcLFnEyAGVDL/k47Jfbm0A=
 github.com/golang/protobuf v1.2.0/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
-github.com/golang/protobuf v1.3.1 h1:YF8+flBXS5eO826T4nzqPrxfhQThhXl0YzfuUPu4SBg=
 github.com/golang/protobuf v1.3.1/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
 github.com/golang/protobuf v1.3.2/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
 github.com/golang/protobuf v1.4.0-rc.1/go.mod h1:ceaxUfeHdC40wWswd/P6IGgMaK3YpKi5j83Wpe3EHw8=
@@ -27,30 +27,40 @@ github.com/golang/protobuf v1.4.2/go.mod h1:oDoupMAO8OvCJWAcko0GGGIgR6R6ocIYbsSw
 github.com/golang/protobuf v1.4.3 h1:JjCZWpVbqXDqFVmTfYWEVTMIYrL/NPdPSCHPJ0T/raM=
 github.com/golang/protobuf v1.4.3/go.mod h1:oDoupMAO8OvCJWAcko0GGGIgR6R6ocIYbsSw735rRwI=
 github.com/google/go-cmp v0.2.0/go.mod h1:oXzfMopK8JAjlY9xF4vHSVASa0yLyX7SntLO5aqRK0M=
-github.com/google/go-cmp v0.3.0 h1:crn/baboCvb5fXaQ0IJ1SGTsTVrWpDsCWC8EGETZijY=
 github.com/google/go-cmp v0.3.0/go.mod h1:8QqcDgzrUqlUb/G2PQTWiueGozuR1884gddMywk6iLU=
 github.com/google/go-cmp v0.3.1/go.mod h1:8QqcDgzrUqlUb/G2PQTWiueGozuR1884gddMywk6iLU=
 github.com/google/go-cmp v0.4.0/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
 github.com/google/go-cmp v0.5.0 h1:/QaMHBdZ26BB3SSst0Iwl10Epc+xhTquomWX0oZEB6w=
 github.com/google/go-cmp v0.5.0/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
 github.com/google/uuid v1.1.2/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
+github.com/kisielk/errcheck v1.5.0/go.mod h1:pFxgyoBC7bSaBwPgfKdkLd5X25qrDl4LWUI2bnpBCr8=
+github.com/kisielk/gotool v1.0.0/go.mod h1:XhKaO+MFFWcvkIS/tQcRk01m1F5IRFswLeQ+oQHNcck=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/prometheus/client_model v0.0.0-20190812154241-14fe0d1b01d4/go.mod h1:xMI15A0UPsDsEKsMN9yxemIoYk6Tm2C1GtYGdfGttqA=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/testify v1.4.0/go.mod h1:j7eGeouHqKxXV5pUuKE4zz7dFj8WfuZ+81PSLYec5m4=
 github.com/stretchr/testify v1.5.1/go.mod h1:5W2xD1RspED5o8YsWQXVCued0rvSQ+mT+I5cxcmMvtA=
+github.com/yuin/goldmark v1.1.27/go.mod h1:3hX8gzYuyVAZsxl0MRgGTJEmQBFcNTphYh9decYSb74=
+github.com/yuin/goldmark v1.2.1/go.mod h1:3hX8gzYuyVAZsxl0MRgGTJEmQBFcNTphYh9decYSb74=
 go.opencensus.io v0.22.5 h1:dntmOdLpSpHlVqbW5Eay97DelsZHe+55D+xC6i0dDS0=
 go.opencensus.io v0.22.5/go.mod h1:5pWMHQbX5EPX2/62yrJeAkowc+lfs/XD7Uxpq3pI6kk=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
+golang.org/x/crypto v0.0.0-20191011191535-87dc89f01550/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
+golang.org/x/crypto v0.0.0-20200622213623-75b288015ac9/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=
 golang.org/x/exp v0.0.0-20190121172915-509febef88a4/go.mod h1:CJ0aWSM057203Lf6IL+f9T1iT9GByDxfZKAQTCR3kQA=
 golang.org/x/lint v0.0.0-20181026193005-c67002cb31c3/go.mod h1:UVdnD1Gm6xHRNCYTkRU2/jEulfH38KcIWyp/GAMgvoE=
 golang.org/x/lint v0.0.0-20190227174305-5b3e6a55c961/go.mod h1:wehouNa3lNwaWXcvxsM5YxQ5yQlVC4a0KAMCusXpPoU=
 golang.org/x/lint v0.0.0-20190313153728-d0100b6bd8b3/go.mod h1:6SW0HCj/g11FgYtHlgUYUwCkIfeOF89ocIRzGO/8vkc=
+golang.org/x/mod v0.2.0/go.mod h1:s0Qsj1ACt9ePp/hMypM3fl4fZqREWJwdYDEqhRiZZUA=
+golang.org/x/mod v0.3.0/go.mod h1:s0Qsj1ACt9ePp/hMypM3fl4fZqREWJwdYDEqhRiZZUA=
 golang.org/x/net v0.0.0-20180724234803-3673e40ba225/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
 golang.org/x/net v0.0.0-20180826012351-8a410e7b638d/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
 golang.org/x/net v0.0.0-20190213061140-3a22650c66bd/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
 golang.org/x/net v0.0.0-20190311183353-d8887717615a/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
+golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
 golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
+golang.org/x/net v0.0.0-20200226121028-0de0cce0169b/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
+golang.org/x/net v0.0.0-20201021035429-f5854403a974/go.mod h1:sp8m0HH+o8qH0wwXwYZr8TS3Oi6o0r6Gce1SSxlDquU=
 golang.org/x/net v0.0.0-20210119194325-5f4716e94777 h1:003p0dJM77cxMSyCPFphvZf/Y5/NXf5fzg6ufd1/Oew=
 golang.org/x/net v0.0.0-20210119194325-5f4716e94777/go.mod h1:m0MpNAwzfU5UDzcl9v0D8zg8gWTRqZa9RBIspLL5mdg=
 golang.org/x/oauth2 v0.0.0-20180821212333-d2e6202438be/go.mod h1:N/0e6XlmueqKjAGxoOufVs8QHGRruUQn6yWY3a++T0U=
@@ -58,10 +68,13 @@ golang.org/x/sync v0.0.0-20180314180146-1d60e4601c6f/go.mod h1:RxMgew5VJxzue5/jJ
 golang.org/x/sync v0.0.0-20181108010431-42b317875d0f/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20190227155943-e225da77a7e6/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
+golang.org/x/sync v0.0.0-20190911185100-cd5d95a43a6e/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
+golang.org/x/sync v0.0.0-20201020160332-67f06af15bc9/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sys v0.0.0-20180830151530-49385e6e1522/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
-golang.org/x/sys v0.0.0-20190502145724-3ef323f4f1fd h1:r7DufRZuZbWB7j439YfAzP8RPDa9unLkpwQKUYbIMPI=
+golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20190502145724-3ef323f4f1fd/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20200930185726-fdedc70b468f/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20201119102817-f84b799fce68 h1:nxC68pudNYkKU6jWhgrqdreuFiOQWj1Fs7T3VrH4Pjw=
 golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
@@ -73,18 +86,22 @@ golang.org/x/tools v0.0.0-20190114222345-bf090417da8b/go.mod h1:n7NCudcB/nEzxVGm
 golang.org/x/tools v0.0.0-20190226205152-f727befe758c/go.mod h1:9Yl7xja0Znq3iFh3HoIrodX9oNMXvdceNzlUR8zjMvY=
 golang.org/x/tools v0.0.0-20190311212946-11955173bddd/go.mod h1:LCzVGOaR6xXOjkQ3onu1FJEFr0SW1gC7cKk1uF8kGRs=
 golang.org/x/tools v0.0.0-20190524140312-2c0ae7006135/go.mod h1:RgjU9mgBXZiqYHBnxXauZ1Gv1EHHAz9KjViQ78xBX0Q=
+golang.org/x/tools v0.0.0-20191119224855-298f0cb1881e/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
+golang.org/x/tools v0.0.0-20200619180055-7c47624df98f/go.mod h1:EkVYQZoAsY45+roYkvgYkIh4xh/qjgUK9TdY2XT94GE=
+golang.org/x/tools v0.0.0-20210106214847-113979e3529a/go.mod h1:emZCQorbCU4vsT4fOWvOPXz4eW1wZW4PmDk9uLelYpA=
+golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
+golang.org/x/xerrors v0.0.0-20191011141410-1b5146add898/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543 h1:E7g+9GITq07hpfrRu66IVDexMakfv52eLZ2CXBWiKr4=
 golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
+golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 google.golang.org/appengine v1.1.0/go.mod h1:EbEs0AVv82hx2wNQdGPgUI5lhzA/G0D9YwlJXL52JkM=
 google.golang.org/appengine v1.4.0/go.mod h1:xpcJRLb0r/rnEns0DIKYYv+WjYCduHsrkT7/EB5XEv4=
 google.golang.org/genproto v0.0.0-20180817151627-c66870c02cf8/go.mod h1:JiN7NxoALGmiZfu7CAH4rXhgtRTLTxftemlI0sWmxmc=
-google.golang.org/genproto v0.0.0-20190425155659-357c62f0e4bb h1:i1Ppqkc3WQXikh8bXiwHqAN5Rv3/qDCcRk0/Otx73BY=
 google.golang.org/genproto v0.0.0-20190425155659-357c62f0e4bb/go.mod h1:VzzqZJRnGkLBvHegQrXjBqPurQTc5/KpmUdxsrq26oE=
 google.golang.org/genproto v0.0.0-20190819201941-24fa4b261c55/go.mod h1:DMBHOl98Agz4BDEuKkezgsaosCRResVns1a3J2ZsMNc=
 google.golang.org/genproto v0.0.0-20200526211855-cb27e3aa2013 h1:+kGHl1aib/qcwaRi1CbqBZ1rk19r85MNUf8HaBghugY=
 google.golang.org/genproto v0.0.0-20200526211855-cb27e3aa2013/go.mod h1:NbSheEEYHJ7i3ixzK3sjbqSGDJWnxyFXZblF3eUsNvo=
 google.golang.org/grpc v1.19.0/go.mod h1:mqu4LbDTu4XGKhr4mRzUsmM4RtVoemTSY81AxZiDr8c=
-google.golang.org/grpc v1.20.1 h1:Hz2g2wirWK7H0qIIhGIqRGTuMwTE8HEKFnDZZ7lm9NU=
 google.golang.org/grpc v1.20.1/go.mod h1:10oTOabMzJvdu6/UiuZezV6QK5dSlG84ov/aaiqXj38=
 google.golang.org/grpc v1.23.0/go.mod h1:Y5yQAOtifL1yxbo5wqy6BxZv8vAUGQwXBOALyacEbxg=
 google.golang.org/grpc v1.25.1/go.mod h1:c3i+UQWmh7LiEpx4sFZnkU36qjEYZ0imhYfXVyQciAY=
diff --git a/grpc/grpc_test.go b/grpc/grpc_test.go
index 625aee7e..500387e3 100644
--- a/grpc/grpc_test.go
+++ b/grpc/grpc_test.go
@@ -24,6 +24,7 @@ import (
 	"strconv"
 	"sync"
 	"testing"
+	"time"
 
 	gc "github.com/vimeo/galaxycache"
 
@@ -79,10 +80,15 @@ func TestGRPCPeerServer(t *testing.T) {
 		if err := g.Get(ctx, key, &value); err != nil {
 			t.Fatal(err)
 		}
-		if string(value) != ":"+key {
-			t.Errorf("Unexpected value: Get(%q) = %q, expected %q", key, value, ":"+key)
+
+		ret, _, err := value.MarshalBinary()
+		if err != nil {
+			t.Fatal(err)
+		}
+		if string(ret) != ":"+key {
+			t.Errorf("Unexpected value: Get(%q) = %q, expected %q", key, ret, ":"+key)
 		}
-		t.Logf("Get key=%q, value=%q (peer:key)", key, value)
+		t.Logf("Get key=%q, value=%q (peer:key)", key, ret)
 	}
 	cancel()
 	wg.Wait()
@@ -104,7 +110,7 @@ func runTestPeerGRPCServer(ctx context.Context, t testing.TB, addresses []string
 	}
 
 	getter := gc.GetterFunc(func(ctx context.Context, key string, dest gc.Codec) error {
-		dest.UnmarshalBinary([]byte(":" + key))
+		dest.UnmarshalBinary([]byte(":"+key), time.Now().Add(5*time.Minute))
 		return nil
 	})
 	universe.NewGalaxy("peerFetchTest", 1<<20, getter)
diff --git a/grpc/grpcclient.go b/grpc/grpcclient.go
index d39f4c94..de42e1f0 100644
--- a/grpc/grpcclient.go
+++ b/grpc/grpcclient.go
@@ -18,6 +18,7 @@ package grpc
 
 import (
 	"context"
+	"time"
 
 	gc "github.com/vimeo/galaxycache"
 	pb "github.com/vimeo/galaxycache/galaxycachepb"
@@ -70,7 +71,7 @@ func (gp *GRPCFetchProtocol) NewFetcher(address string) (gc.RemoteFetcher, error
 
 // Fetch here implements the RemoteFetcher interface for
 // sending Gets to peers over an RPC connection
-func (g *grpcFetcher) Fetch(ctx context.Context, galaxy string, key string) ([]byte, error) {
+func (g *grpcFetcher) Fetch(ctx context.Context, galaxy string, key string) ([]byte, time.Time, error) {
 	span := trace.FromContext(ctx)
 	span.Annotatef(nil, "fetching from %s; connection state %s", g.address, g.conn.GetState())
 	resp, err := g.client.GetFromPeer(ctx, &pb.GetRequest{
@@ -78,10 +79,10 @@ func (g *grpcFetcher) Fetch(ctx context.Context, galaxy string, key string) ([]b
 		Key:    key,
 	})
 	if err != nil {
-		return nil, status.Errorf(status.Code(err), "Failed to fetch from peer over RPC [%q, %q]: %s", galaxy, g.address, err)
+		return nil, time.Time{}, status.Errorf(status.Code(err), "Failed to fetch from peer over RPC [%q, %q]: %s", galaxy, g.address, err)
 	}
 
-	return resp.Value, nil
+	return resp.Value, time.UnixMilli(resp.Expire), nil
 }
 
 // Close here implements the RemoteFetcher interface for
diff --git a/grpc/grpcserver.go b/grpc/grpcserver.go
index f4b8faf9..c1c80d67 100644
--- a/grpc/grpcserver.go
+++ b/grpc/grpcserver.go
@@ -20,6 +20,7 @@ import (
 	"context"
 
 	gc "github.com/vimeo/galaxycache"
+	"github.com/vimeo/galaxycache/galaxycachepb"
 	pb "github.com/vimeo/galaxycache/galaxycachepb"
 
 	"google.golang.org/grpc"
@@ -31,6 +32,7 @@ import (
 // interface generated by the GalaxyCache pb service
 type serviceImpl struct {
 	universe *gc.Universe
+	galaxycachepb.UnimplementedGalaxyCacheServer
 }
 
 // RegisterGRPCServer registers the given grpc.Server with
@@ -58,5 +60,10 @@ func (gp *serviceImpl) GetFromPeer(ctx context.Context, req *pb.GetRequest) (*pb
 		return nil, status.Errorf(status.Code(err), "Failed to retrieve [%s]: %v", req, err)
 	}
 
-	return &pb.GetResponse{Value: value}, nil
+	ret, expTm, err := value.MarshalBinary()
+	if err != nil {
+		return nil, status.Errorf(status.Code(err), "Failed to marshal [%s]: %v", req, err)
+	}
+
+	return &pb.GetResponse{Value: ret, Expire: expTm.UnixMilli()}, nil
 }
diff --git a/grpc/unsafe_byte_codec.go b/grpc/unsafe_byte_codec.go
index 1ff1d7d0..c215cd76 100644
--- a/grpc/unsafe_byte_codec.go
+++ b/grpc/unsafe_byte_codec.go
@@ -1,17 +1,23 @@
 package grpc
 
+import "time"
+
 // unsafeByteCodec is a byte slice type that implements Codec
-type unsafeByteCodec []byte
+type unsafeByteCodec struct {
+	bytes  []byte
+	expire time.Time
+}
 
 // MarshalBinary returns the contained byte-slice
-func (c *unsafeByteCodec) MarshalBinary() ([]byte, error) {
-	return *c, nil
+func (c *unsafeByteCodec) MarshalBinary() ([]byte, time.Time, error) {
+	return c.bytes, c.expire, nil
 }
 
 // UnmarshalBinary to provided data so they share the same backing array
 // this is a generally unsafe performance optimization, but safe in the context
 // of the gRPC server.
-func (c *unsafeByteCodec) UnmarshalBinary(data []byte) error {
-	*c = data
+func (c *unsafeByteCodec) UnmarshalBinary(data []byte, expire time.Time) error {
+	c.bytes = data
+	c.expire = expire
 	return nil
 }
diff --git a/hotcache.go b/hotcache.go
index 9521734a..f7a9de42 100644
--- a/hotcache.go
+++ b/hotcache.go
@@ -57,14 +57,15 @@ type keyStats struct {
 	dQPS dampedQPS
 }
 
-func newValWithStat(data []byte, kStats *keyStats) *valWithStat {
+func newValWithStat(data []byte, kStats *keyStats, expire time.Time) *valWithStat {
 	if kStats == nil {
 		kStats = &keyStats{dampedQPS{period: time.Second}}
 	}
 
 	return &valWithStat{
-		data:  data,
-		stats: kStats,
+		data:   data,
+		stats:  kStats,
+		expire: expire,
 	}
 }
 
@@ -126,19 +127,19 @@ func (d *dampedQPS) val(now time.Time) float64 {
 	return d.curDQPS
 }
 
-func (g *Galaxy) addNewToCandidateCache(key string) *keyStats {
+func (g *Galaxy) addNewToCandidateCache(key string, expire time.Time) *keyStats {
 	kStats := &keyStats{
 		dQPS: dampedQPS{
 			period: time.Second,
 		},
 	}
 
-	g.candidateCache.addToCandidateCache(key, kStats)
+	g.candidateCache.addToCandidateCache(key, kStats, expire)
 	return kStats
 }
 
-func (c *cache) addToCandidateCache(key string, kStats *keyStats) {
+func (c *cache) addToCandidateCache(key string, kStats *keyStats, expire time.Time) {
 	c.mu.Lock()
 	defer c.mu.Unlock()
-	c.lru.Add(key, kStats)
+	c.lru.Add(key, kStats, expire)
 }
diff --git a/http/http.go b/http/http.go
index 928dad0d..3743bb64 100644
--- a/http/http.go
+++ b/http/http.go
@@ -22,7 +22,9 @@ import (
 	"io/ioutil"
 	"net/http"
 	"net/url"
+	"strconv"
 	"strings"
+	"time"
 
 	gc "github.com/vimeo/galaxycache"
 
@@ -32,6 +34,9 @@ import (
 
 const defaultBasePath = "/_galaxycache/"
 
+// When the retrieved value should expire. Unix timestamp in milliseconds.
+const ttlHeader = "X-Galaxycache-Expire"
+
 // HTTPFetchProtocol specifies HTTP specific options for HTTP-based
 // peer communication
 type HTTPFetchProtocol struct {
@@ -181,7 +186,13 @@ func (h *HTTPHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 	w.Header().Set("Content-Type", "application/octet-stream")
-	w.Write(value)
+	b, expTm, err := value.MarshalBinary()
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+	w.Header().Set(ttlHeader, fmt.Sprintf("%d", expTm.UnixMilli()))
+	w.Write(b)
 }
 
 type httpFetcher struct {
@@ -190,7 +201,7 @@ type httpFetcher struct {
 }
 
 // Fetch here implements the RemoteFetcher interface for sending a GET request over HTTP to a peer
-func (h *httpFetcher) Fetch(ctx context.Context, galaxy string, key string) ([]byte, error) {
+func (h *httpFetcher) Fetch(ctx context.Context, galaxy string, key string) ([]byte, time.Time, error) {
 	u := fmt.Sprintf(
 		"%v%v/%v",
 		h.baseURL,
@@ -199,21 +210,30 @@ func (h *httpFetcher) Fetch(ctx context.Context, galaxy string, key string) ([]b
 	)
 	req, err := http.NewRequest("GET", u, nil)
 	if err != nil {
-		return nil, err
+		return nil, time.Time{}, err
 	}
 	res, err := h.transport.RoundTrip(req.WithContext(ctx))
 	if err != nil {
-		return nil, err
+		return nil, time.Time{}, err
 	}
 	defer res.Body.Close()
 	if res.StatusCode != http.StatusOK {
-		return nil, fmt.Errorf("server returned HTTP response status code: %v", res.Status)
+		return nil, time.Time{}, fmt.Errorf("server returned HTTP response status code: %v", res.Status)
 	}
 	data, err := ioutil.ReadAll(res.Body)
 	if err != nil {
-		return nil, fmt.Errorf("reading response body: %v", err)
+		return nil, time.Time{}, fmt.Errorf("reading response body: %v", err)
+	}
+
+	expireStr := res.Header[ttlHeader]
+	if len(expireStr) == 0 {
+		return nil, time.Time{}, fmt.Errorf("failed reading TTL header %s", ttlHeader)
+	}
+	expire, err := strconv.ParseInt(expireStr[0], 10, 64)
+	if err != nil {
+		return nil, time.Time{}, fmt.Errorf("parsing TTL header %s: %w", ttlHeader, err)
 	}
-	return data, nil
+	return data, time.UnixMilli(expire), nil
 }
 
 // Close here implements the RemoteFetcher interface for closing (does nothing for HTTP)
diff --git a/http/http_test.go b/http/http_test.go
index 5c3371b1..46d0c4c5 100644
--- a/http/http_test.go
+++ b/http/http_test.go
@@ -25,6 +25,7 @@ import (
 	"strings"
 	"sync"
 	"testing"
+	"time"
 
 	gc "github.com/vimeo/galaxycache"
 
@@ -86,11 +87,21 @@ func TestHTTPHandler(t *testing.T) {
 				if err := g.Get(ctx, key, &value); err != nil {
 					t.Fatal(err)
 				}
-				if suffix := ":" + key; !strings.HasSuffix(string(value), suffix) {
-					t.Errorf("Get(%q) = %q, want value ending in %q", key, value, suffix)
+				ret, expTm, err := value.MarshalBinary()
+				if err != nil {
+					t.Fatal(err)
+				}
+				if expTm.Equal(time.Time{}) {
+					t.Fatal("expiry time must be set")
 				}
-				t.Logf("Get key=%q, value=%q (peer:key)", key, value)
+				if suffix := ":" + key; !strings.HasSuffix(string(ret), suffix) {
+					t.Errorf("Get(%q) = %q, want value ending in %q", key, ret, suffix)
+				}
+				t.Logf("Get key=%q, value=%q (peer:key)", key, ret)
 			}
+
+			currentExp := time.Now().Add(2 * time.Second)
+			time.Sleep(5 * time.Second)
 			// Try it again, this time with a slash in the middle to ensure we're
 			// handling those characters properly
 			for _, key := range testKeys(nGets) {
@@ -99,10 +110,19 @@ func TestHTTPHandler(t *testing.T) {
 				if err := g.Get(ctx, testKey, &value); err != nil {
 					t.Fatal(err)
 				}
-				if suffix := ":" + testKey; !strings.HasSuffix(string(value), suffix) {
-					t.Errorf("Get(%q) = %q, want value ending in %q", key, value, suffix)
+				ret, expTm, err := value.MarshalBinary()
+				if err != nil {
+					t.Fatal(err)
+				}
+
+				// Ensure that the keys were regenerated.
+				if expTm.Before(currentExp) {
+					t.Fatalf("expected key to expire after the current time i.e. it should be regenerated (%s, %s)", expTm, currentExp)
+				}
+				if suffix := ":" + testKey; !strings.HasSuffix(string(ret), suffix) {
+					t.Errorf("Get(%q) = %q, want value ending in %q", key, ret, suffix)
 				}
-				t.Logf("Get key=%q, value=%q (peer:key)", testKey, value)
+				t.Logf("Get key=%q, value=%q (peer:key)", testKey, ret)
 			}
 
 		})
@@ -119,7 +139,7 @@ func makeHTTPServerUniverse(ctx context.Context, t testing.TB, galaxyName string
 		t.Errorf("Error setting peers: %s", err)
 	}
 	getter := gc.GetterFunc(func(ctx context.Context, key string, dest gc.Codec) error {
-		dest.UnmarshalBinary([]byte(":" + key))
+		dest.UnmarshalBinary([]byte(":"+key), time.Now().Add(2*time.Second))
 		return nil
 	})
 	universe.NewGalaxy(galaxyName, 1<<20, getter)
diff --git a/lru/lru.go b/lru/lru.go
index a9f42c3f..11176448 100644
--- a/lru/lru.go
+++ b/lru/lru.go
@@ -19,6 +19,7 @@ package lru // import "github.com/vimeo/galaxycache/lru"
 
 import (
 	"container/list"
+	"time"
 )
 
 // Cache is an LRU cache. It is not safe for concurrent access.
@@ -39,8 +40,9 @@ type Cache struct {
 type Key interface{}
 
 type entry struct {
-	key   Key
-	value interface{}
+	key    Key
+	value  interface{}
+	expire time.Time
 }
 
 // New creates a new Cache.
@@ -55,7 +57,7 @@ func New(maxEntries int) *Cache {
 }
 
 // Add adds a value to the cache.
-func (c *Cache) Add(key Key, value interface{}) {
+func (c *Cache) Add(key Key, value interface{}, expire time.Time) {
 	if c.cache == nil {
 		c.cache = make(map[interface{}]*list.Element)
 		c.ll = list.New()
@@ -65,7 +67,7 @@ func (c *Cache) Add(key Key, value interface{}) {
 		ele.Value.(*entry).value = value
 		return
 	}
-	ele := c.ll.PushFront(&entry{key, value})
+	ele := c.ll.PushFront(&entry{key, value, expire})
 	c.cache[key] = ele
 	if c.MaxEntries != 0 && c.ll.Len() > c.MaxEntries {
 		c.RemoveOldest()
@@ -78,8 +80,15 @@ func (c *Cache) Get(key Key) (value interface{}, ok bool) {
 		return
 	}
 	if ele, hit := c.cache[key]; hit {
+		entry := ele.Value.(*entry)
+		// If the entry has expired, remove it from the cache
+		if !entry.expire.IsZero() && entry.expire.Before(time.Now()) {
+			c.removeElement(ele)
+			return nil, false
+		}
+
 		c.ll.MoveToFront(ele)
-		return ele.Value.(*entry).value, true
+		return entry.value, true
 	}
 	return
 }
diff --git a/lru/lru_test.go b/lru/lru_test.go
index 870fe38c..16622f59 100644
--- a/lru/lru_test.go
+++ b/lru/lru_test.go
@@ -19,6 +19,7 @@ package lru
 import (
 	"fmt"
 	"testing"
+	"time"
 )
 
 type simpleStruct struct {
@@ -48,7 +49,7 @@ func TestGet(t *testing.T) {
 
 	for _, tt := range getTests {
 		lru := New(0)
-		lru.Add(tt.keyToAdd, 1234)
+		lru.Add(tt.keyToAdd, 1234, time.Time{})
 		val, ok := lru.Get(tt.keyToGet)
 		if ok != tt.expectedOk {
 			t.Fatalf("%s: cache hit = %v; want %v", tt.name, ok, !ok)
@@ -60,7 +61,7 @@ func TestGet(t *testing.T) {
 
 func TestRemove(t *testing.T) {
 	lru := New(0)
-	lru.Add("myKey", 1234)
+	lru.Add("myKey", 1234, time.Time{})
 	if val, ok := lru.Get("myKey"); !ok {
 		t.Fatal("TestRemove returned no match")
 	} else if val != 1234 {
@@ -82,7 +83,7 @@ func TestEvict(t *testing.T) {
 	lru := New(20)
 	lru.OnEvicted = onEvictedFun
 	for i := 0; i < 22; i++ {
-		lru.Add(fmt.Sprintf("myKey%d", i), 1234)
+		lru.Add(fmt.Sprintf("myKey%d", i), 1234, time.Time{})
 	}
 
 	if len(evictedKeys) != 2 {
@@ -95,3 +96,28 @@ func TestEvict(t *testing.T) {
 		t.Fatalf("got %v in second evicted key; want %s", evictedKeys[1], "myKey1")
 	}
 }
+
+func TestExpire(t *testing.T) {
+	var tests = []struct {
+		name       string
+		key        interface{}
+		expectedOk bool
+		expire     time.Duration
+		wait       time.Duration
+	}{
+		{"not-expired", "myKey", true, time.Second * 1, time.Duration(0)},
+		{"expired", "expiredKey", false, time.Millisecond * 100, time.Millisecond * 150},
+	}
+
+	for _, tt := range tests {
+		lru := New(0)
+		lru.Add(tt.key, 1234, time.Now().Add(tt.expire))
+		time.Sleep(tt.wait)
+		val, ok := lru.Get(tt.key)
+		if ok != tt.expectedOk {
+			t.Fatalf("%s: cache hit = %v; want %v", tt.name, ok, !ok)
+		} else if ok && val != 1234 {
+			t.Fatalf("%s expected get to return 1234 but got %v", tt.name, val)
+		}
+	}
+}
diff --git a/peers.go b/peers.go
index bf86733c..57f78cb9 100644
--- a/peers.go
+++ b/peers.go
@@ -28,6 +28,7 @@ import (
 	"errors"
 	"fmt"
 	"sync"
+	"time"
 
 	"github.com/vimeo/galaxycache/consistenthash"
 )
@@ -38,7 +39,8 @@ const defaultReplicas = 50
 // other peers; the PeerPicker contains a map of these fetchers corresponding
 // to each other peer address
 type RemoteFetcher interface {
-	Fetch(context context.Context, galaxy string, key string) ([]byte, error)
+	// The value and when it should expire.
+	Fetch(context context.Context, galaxy string, key string) ([]byte, time.Time, error)
 	// Close closes a client-side connection (may be a nop)
 	Close() error
 }
@@ -166,8 +168,8 @@ func (n *NullFetchProtocol) NewFetcher(url string) (RemoteFetcher, error) {
 
 type nullFetchFetcher struct{}
 
-func (n *nullFetchFetcher) Fetch(context context.Context, galaxy string, key string) ([]byte, error) {
-	return nil, errors.New("empty fetcher")
+func (n *nullFetchFetcher) Fetch(context context.Context, galaxy string, key string) ([]byte, time.Time, error) {
+	return nil, time.Time{}, errors.New("empty fetcher")
 }
 
 // Close closes a client-side connection (may be a nop)
diff --git a/proto.sh b/proto.sh
new file mode 100644
index 00000000..4927f6d4
--- /dev/null
+++ b/proto.sh
@@ -0,0 +1,2 @@
+#!/bin/bash
+protoc  --go-grpc_out=. --proto_path=galaxycachepb --go_out=galaxycachepb --go_opt=paths=source_relative galaxycache.proto