Currently on disagg standby, write operations (insert, update and deletes) perform an extra lookup on the stable table to check for duplicate keys before writing to the ingest table. Due to cold cache and the current limitation where WT doesn't share unmodified pages between checkpoints, these stable pages have to be fetched from Page server. This adds latency to write operation and negatively impacts standby performance.

For now, we'd like to enable blind writes for both collection and the index tables by having mongod create cursors with overwrite=true (see here). This would skip the stable table lookup during writes.

For debug builds, we'd keep non-blind writes (with the stable lookup) to catch potential issues. In production, we'd enable blind writes by default but probabilistically fall back to non-blind writes for a small percentage of operations (~1%) as a safety check.