Durable Objects, Workers - New Best Practices guide for Durable Objects

A new Rules of Durable Objects guide is now available, providing opinionated best practices for building effective Durable Objects applications. This guide covers design patterns, storage strategies, concurrency, and common anti-patterns to avoid. Key guidance includes: Design around your "atom" of coordination — Create one Durable Object per logical unit (chat room, game session, user) instead of a global singleton that becomes a bottleneck. Use SQLite storage with RPC methods — SQLite-backed Durable Objects with typed RPC methods provide the best developer experience and performance. Understand input and output gates — Learn how Cloudflare's runtime prevents data races by default, how write coalescing works, and when to use blockConcurrencyWhile() . Leverage Hibernatable WebSockets — Reduce costs for real-time applications by allowing Durable Objects to sleep while maintaining WebSocket connections. The testing documentation has also been updated with modern patterns using @cloudflare/vitest-pool-workers , including examples for testing SQLite storage, alarms, and direct instance access: JavaScript import { env , runDurableObjectAlarm } from "cloudflare:test" ; import { it , expect } from "vitest" ; it ( "can test Durable Objects with isolated storage" , async () => { const stub = env . COUNTER . getByName ( "test" ) ; // Call RPC methods directly on the stub await stub . increment () ; expect ( await stub . getCount ()) . toBe ( 1 ) ; // Trigger alarms immediately without waiting await runDurableObjectAlarm ( stub ) ; } ) ; TypeScript import { env , runDurableObjectAlarm } from "cloudflare:test" ; import { it , expect } from "vitest" ; it ( "can test Durable Objects with isolated storage" , async () => { const stub = env . COUNTER . getByName ( "test" ) ; // Call RPC methods directly on the stub await stub . increment () ; expect ( await stub . getCount ()) . toBe ( 1 ) ; // Trigger alarms immediately without waiting await runDurableObjectAlarm ( stub ) ; } )