Write-Ahead Log
Provide durability guarantee without the storage data structures to be flushed to disk, by persisting every state change as a command to the append only log.
aka: Commit Log
Problem
Strong durability guarantee is needed even in the case of the server machines storing data failing. Once a server agrees to perform an action, it should do so even if it fails and restarts losing all of its in-memory state.
Solution
Store each state change as a command in a file on a hard disk.
for more details go to Chapter 03 of the online ebook at oreilly.com
This pattern is part of Patterns of Distributed Systems
23 November 2023