Overview

Remove the intermediate apply-at-commit step from the staged-write commit path, so the primary's WiredTiger transaction commits only the oplog entry. Collection and index writes are applied later by primary oplog application.

Background

The commit path initially replays the staged buffer into WiredTiger inside the commit critical section (design note section 7, step 3). That keeps storage writes on the critical path. The oplog entry is already built from the OpObserver's logical operations (design note appendix A), not from the buffer, so oplog generation does not change.

Scope of Work

• Skip the staged-buffer replay at commit; commit only the oplog entry, preserving visibility, hole and allDurable tracking.
• Cover single-document writes and multi-document transactions, including transactions that span multiple oplog entries.
• Basic jstests on non-conflicting workloads (e.g. YCSB load).

Acceptance Criteria

• Staged writes produce correct oplog entries and no collection/index writes on the primary at commit time.
• Findings recorded on this ticket.

Technical Notes

• Prototype quality; not intended for commit to master.
• Design reference: src/mongo/db/txns/staged_writes_design.md (PR #66680).