Summary

Build the core asynchronous step-down logic in WiredTiger to handle concurrent reads and writes during the step-down process.

Motivation

During a step-down, WiredTiger must transition from read-write to read-only mode without blocking or corrupting in-flight CRUD cursor operations. This ticket covers the core async step-down path for standard cursor operations (insert, update, remove, search, scan).

Scope

This ticket covers:
- Core async read and write logic during the step-down transition
- CRUD cursor operations (insert, update, remove, search, scan) running concurrently with step-down

This ticket explicitly excludes:
- Fast truncate support (future sprint)
- Prepared transaction support (Sprint 2)

Definition of Done

• Core async read and write logic is fully supported during the step-down transition
• CRUD cursor operations complete correctly or return a well-defined error when a step-down occurs concurrently
• Existing Python and C test suites pass with the new logic enabled