The latest articles on DEV Community by Harper Ward (@harper_ships). https://dev.to/harper_ships https://media2.dev.to/dynamic/image/width=90,height=90,fit=cover,gravity=auto,format=auto/https:%2F%2Fdev-to-uploads.s3.us-east-2.amazonaws.com%2Fuploads%2Fuser%2Fprofile_image%2F4210908%2Fed2dbc15-bff3-4228-9d41-3712c882cd84.jpg https://dev.to/harper_ships en Harper Ward Tue, 27 Oct 2026 15:49:49 +0000 https://dev.to/harper_ships/reading-sqlites-wal-a-devops-detour-59b5 https://dev.to/harper_ships/reading-sqlites-wal-a-devops-detour-59b5 <p>A small service started getting <code>database is locked</code> errors under load. The fix was a one-line change to the busy timeout, but understanding <em>why</em> took longer.</p> <p>What I learned about SQLite's WAL mode:</p> <ul> <li>Writers append to a WAL file; readers don't block writers</li> <li>Checkpoints move WAL pages back into the main database</li> <li>A long-running reader can delay a checkpoint and grow the WAL</li> </ul> <p>That last point explained our problem: an analytics query held a read transaction open, and the WAL grew until the disk alarm fired. We capped the query and moved it to a replica.</p> <p>I keep coming back to SQLite because the more I learn, the more predictable it gets. That's a rare property in infrastructure.</p> sqlite devops database