langgenius/mosoo-skills/durable-objects
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Create and review Cloudflare Durable Objects. Use when building stateful coordination (chat rooms, multiplayer games, booking systems), implementing RPC methods, SQLite storage, alarms, WebSockets, or reviewing DO code for best practices. Covers Workers integration, wrangler config, and testing with Vitest. Biases towards retrieval from Cloudflare docs over pre-trained knowledge.
Install
npx vskill@latest install langgenius/mosoo-skills/durable-objectsSKILL.md
The same SKILL.md was published earlier as openai/plugins/durable-objects.
Durable Objects
Build stateful, coordinated applications on Cloudflare's edge using Durable Objects.
Retrieval Sources
Your knowledge of Durable Objects APIs and configuration may be outdated. Prefer retrieval over pre-training for any Durable Objects task.
| Resource | URL | |
|---|---|---|
| Docs | https://developers.cloudflare.com/durable-objects/ | |
| API Reference | https://developers.cloudflare.com/durable-objects/api/ | |
| Best Practices | https://developers.cloudflare.com/durable-objects/best-practices/ | |
| Examples | https://developers.cloudflare.com/durable-objects/examples/ |
Fetch the relevant doc page when implementing features.
When to Use
- Creating new Durable Object classes for stateful coordination
- Implementing RPC methods, alarms, or WebSocket handlers
- Reviewing existing DO code for best practices
- Configuring wrangler.jsonc/toml for DO bindings and migrations
- Writing tests with
@cloudflare/vitest-pool-workers - Designing sharding strategies and parent-child relationships
Reference Documentation
./references/rules.md- Core rules, storage, concurrency, RPC, alarms./references/testing.md- Vitest setup, unit/integration tests, alarm testing./references/workers.md- Workers handlers, types, wrangler config, observability
Search: blockConcurrencyWhile, idFromName, getByName, setAlarm, sql.exec
Core Principles
Use Durable Objects For
| Need | Example | |
|---|---|---|
| Coordination | Chat rooms, multiplayer games, collaborative docs | |
| Strong consistency | Inventory, booking systems, turn-based games | |
| Per-entity storage | Multi-tenant SaaS, per-user data | |
| Persistent connections | WebSockets, real-time notifications | |
| Scheduled work per entity | Subscription renewals, game timeouts |
Do NOT Use For
- Stateless request handling (use plain Workers)
- Maximum global distribution needs
- High fan-out independent requests
Quick Reference
Wrangler Configuration
Basic Durable Object Pattern
Critical Rules
- Model around coordination atoms - One DO per chat room/game/user, not one global DO
- Use `getByName()` for deterministic routing - Same input = same DO instance
- Use SQLite storage - Configure
new_sqlite_classesin migrations - Initialize in constructor - Use
blockConcurrencyWhile()for schema setup only - Use RPC methods - Not fetch() handler (compatibility date >= 2024-04-03)
- Persist first, cache second - Always write to storage before updating in-memory state
- One alarm per DO -
setAlarm()replaces any existing alarm
Anti-Patterns (NEVER)
- Single global DO handling all requests (bottleneck)
- Using
blockConcurrencyWhile()on every request (kills throughput) - Storing critical state only in memory (lost on eviction/crash)
- Using
awaitbetween related storage writes (breaks atomicity) - Holding
blockConcurrencyWhile()acrossfetch()or external I/O
Stub Creation
Storage Operations
Alarms
Testing Quick Start
Security
- Security scanPassed, 95 of 100Pattern checks on the skill's files.
- Model reviewPassed
Quality evaluation
- Task evaluationNot runNo evaluation yet. Run one in Skill Studio.
Source
- SKILL.md in the repositoryCheckingskills/durable-objects/SKILL.md
Popularity
- 7-day trend score
- 5
Not refreshed yet.
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