If you are building local-first applications, using SQLite in edge environments, or utilizing it as a microservice persistence layer, you have likely encountered this error: sqlite3.OperationalError: database is locked This error is often misunderstood as a limitation of SQLite itself. It is not. It is a configuration issue. By default, SQLite is optimized for maximum compatibility and safety, not for high-concurrency throughput. When multiple processes (e.g., Gunicorn workers in Python or clustered Node.js instances) attempt to write to the database simultaneously, the default locking mechanism fails. This post details the root cause of lock contention and provides the production-grade configuration to resolve it using Write-Ahead Logging (WAL). The Root Cause: Rollback Journals and Exclusive Locking To fix the error, you must understand the default behavior: the Rollback Journal . In the default mode ( journal_mode = DELETE ), SQLite uses a pessimistic locking strategy to...
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