diff --git a/docs/design/mysql_storage.md b/docs/design/mysql_storage.md
index 9d3c83b3..9b8badcd 100644
--- a/docs/design/mysql_storage.md
+++ b/docs/design/mysql_storage.md
@@ -26,10 +26,6 @@ An internal tile consisting of hashes. There is one row for each internal tile,
 #### `TiledLeaves`
 
 The data committed to by the leaves of the tree. Follows the same evolution as Subtree.
-
-#### `HashIndex`
-
-An optional table that allows deduplication to be implemented efficiently.
  
 Reads can scale horizontally with very little overhead or contention between frontends.
 
diff --git a/storage/mysql/mysql.go b/storage/mysql/mysql.go
index bd7dd01b..b8b1285f 100644
--- a/storage/mysql/mysql.go
+++ b/storage/mysql/mysql.go
@@ -217,8 +217,6 @@ func (s *Storage) writeEntryBundle(ctx context.Context, tx *sql.Tx, index uint64
 
 // Add is the entrypoint for adding entries to a sequencing log.
 func (s *Storage) Add(ctx context.Context, entry *tessera.Entry) (uint64, error) {
-	// TODO(#21): Return index if the value is already stored.
-
 	return s.queue.Add(ctx, entry)()
 }