latestBlock

The latest block this database has durable in object storage, or null before its first block.

This advances only once the block's file has landed in storage, so a source may treat the emitted BlockDetails.externalSourceToken as the furthest position it is safe to confirm upstream. Confirming past it tells the upstream to discard data that exists only in the replica log and the leader's live index — which the upstream cannot then re-send.

Note this necessarily lags submitTx's durability handle, which completes once the transaction is replicated and applied. A source that acknowledges per-transaction is therefore acknowledging a position storage does not yet hold.