durable-objects

Extend the DurableObject class from cloudflare:workers and configure new_sqlite_classes in your wrangler migrations. Initialize tables inside the constructor using ctx.blockConcurrencyWhile and run synchronous queries with ctx.storage.sql.exec.

Use @cloudflare/vitest-pool-workers with defineWorkersConfig pointing at your wrangler config. Access stubs via env from cloudflare:test, inspect internals with runInDurableObject, and trigger alarms instantly with runDurableObjectAlarm.

Use Durable Objects when you need coordination, strong consistency, per-entity storage, persistent WebSocket connections, or per-entity scheduled work. Plain Workers are better for stateless request handling and maximum global distribution.

No, PRAGMA user_version is not supported in Durable Objects SQLite storage. Track schema versions in a dedicated _sql_schema_migrations table and apply incremental migrations during constructor initialization.

A single global DO instance serializes all requests and limits throughput. Model one DO per coordination atom such as a room or user using getByName, and avoid calling blockConcurrencyWhile on every request.

Each DO supports one alarm at a time, and setAlarm replaces any existing alarm. Implement the alarm handler method to process scheduled work, reschedule as needed, and keep handlers idempotent since failed alarms auto-retry.