explanation

Author: benesjan

yarn-project/pxe/src/tagging/sync/sync_sender_tagging_indexes.ts

@@ -50,9 +50,16 @@ export async function syncSenderTaggingIndexes(
   // hard limit we give a guarantee to a recipient that he doesn't need to look further than WINDOW_LEN ahead of the
   // highest finalized index.
   //
-  // This function synchronizes these two values by iteratively querying the node for a window of indexes at a time,
-  // storing all those indexes as pending, and then checking the status of each pending index to update its
-  // finalization status accordingly.
+  // This function synchronizes the finalized and pending indexes by iteratively querying the node for a window of
+  // indexes at a time, storing all those indexes as pending, and then checking the status of each pending index to
+  // update its finalization status accordingly. If we stumble upon a window with no indexes, we stop the loop.
+  //
+  // Stopping at that point is safe because of the limit described above - there can never be an index that is more
+  // than WINDOW_LEN from the highest finalized index.
+  //
+  // # Note on performance
+  // Each window advance requires two queries (logs + tx status). For example, syncing indexes 0–500 with a window of
+  // 100 takes at least 10 round trips (5 windows × 2 queries).
 
   const finalizedIndex = await taggingDataProvider.getLastFinalizedIndex(secret);