Also known as

• Append-Only Log
• Redo Log
• Journaling

Intent of Write-Ahead Log Pattern

The Write-Ahead Log (WAL) design pattern ensures data durability and system recoverability in database engines, distributed consensus protocols, and transactional systems. It enforces a strict order of operations where any state mutation (e.g., insert, update, delete) must be written sequentially to an append-only log file on stable storage (disk) before it is applied to the main database state or in-memory storage structures.