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


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.


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