Write-Ahead Log

Definitions

1. A durability technique where changes are first written to an append-only log before being applied to the main data structure. If the system crashes mid-write, it can replay the log to recover. Used by PostgreSQL, SQLite, and most databases.

   In plain English: Writing down what you're about to change in a log before actually changing it, so you can recover if something goes wrong.

   Example: "PostgreSQL's WAL ensures no committed transaction is lost — even if the server crashes, it replays the log on restart."

Related Terms

• Webhook vs. Polling
• Event-Driven Architecture
• Circuit Breaker
• Consistency
• Tombstone
• Connection Pooling
• WAL Replay
• Upsert