Status: IN
With `async_index=True`, `TermPartitionedDB` queues index operations in `_pending` instead of applying them immediately; `flush_index()` must be called to drain the queue, modeling asynchronous global index updates.
Source: entries/2026/05/29/secondary-index-partitioning-secondary_index_partitioning.md
self._pending_updates.append((field, value, doc_id))
# index not updated until flush/apply