From 8697d1932918b290f2ea20a2f550414e57501323 Mon Sep 17 00:00:00 2001
From: James Wilson <james@jsdw.me>
Date: Mon, 4 Dec 2023 11:57:40 +0000
Subject: [PATCH] add small comment

---
 subxt/src/backend/unstable/mod.rs | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/subxt/src/backend/unstable/mod.rs b/subxt/src/backend/unstable/mod.rs
index 05b78cbd89..fb1437352d 100644
--- a/subxt/src/backend/unstable/mod.rs
+++ b/subxt/src/backend/unstable/mod.rs
@@ -486,6 +486,8 @@ impl<T: Config + Send + Sync + 'static> Backend<T> for UnstableBackend<T> {
                 if let Poll::Ready(Some(seen_block)) = seen_blocks_sub.poll_next_unpin(cx) {
                     match seen_block {
                         SeenBlock::New(block_ref) => {
+                            // Optimization: once we have a `finalized_hash`, we only care about finalized
+                            // block refs now and can avoid bothering to save new blocks.
                             if finalized_hash.is_none() {
                                 seen_blocks
                                     .insert(block_ref.hash(), (SeenBlockMarker::New, block_ref));