Use SQLite for new classes. Existing KV-backed classes need their matching API reference; using key-value methods does not by itself identify the backend.

Fetch the relevant current documentation before implementing or reviewing changes.

Task	Documentation
Choose SQL, key-value access, transactions, or recovery APIs	SQLite storage API; Legacy KV storage API
Configure the backend, class lifecycle, and placement	Configuration
Find operation semantics and storage options	API routing
Design schemas, caches, scheduled work, or cleanup	Patterns
Diagnose concurrency, limits, and billing	Troubleshooting
Verify storage behavior in the Workers runtime	Testing

For object routing, WebSockets, and coordination design, see the Durable Objects skill.