cloudflare-durable-objects

Durable Objects enable stateful WebSocket patterns by maintaining persistent state across connections. Use WebSocket hibernation to pause inactive connections and alarms to trigger events, reducing memory overhead while keeping state synchronized across multiple clients in real-time applications like chat rooms and multiplayer games.

Structure DO classes with proper scaffolding, configure bindings in wrangler, and implement migrations to evolve your data schema safely. Migrations let you transform existing state while maintaining backward compatibility across deployments.

Yes, Durable Objects support SQLite for relational storage alongside KV for key-value data. Choose SQL when you need structured queries and transactions, or KV for simpler state management, depending on your application's data access patterns.

Durable Objects communicate via RPC for direct method invocation or Fetch for HTTP-style requests. RPC offers lower latency for inter-DO coordination in scenarios like cross-room messaging, while Fetch integrates with standard HTTP patterns for broader compatibility.

Alarms trigger scheduled logic without external cron jobs—ideal for rate limiting cleanup, session timeouts, and periodic state synchronization. They execute within the DO's context, preserving consistency for time-sensitive operations.

Yes, Durable Objects excel at session management by maintaining per-user state and rate limiting by tracking request counts with alarms enforcing reset schedules. Their persistent, low-latency state makes them suitable for these stateful, high-concurrency use cases.