cloudflare-durable-objects

Cloudflare Durable Objects

Durable Objects provide strongly consistent, low-latency coordination and state for Workers. Each object is a single-threaded instance with persistent storage, ideal for WebSocket servers, counters, rate limiters, and collaborative apps.

• Docs: https://developers.cloudflare.com/durable-objects/
• Pulumi: Deployed as part of cloudflare.WorkersScript with durableObjectBindings

Durable Object Class

export class Counter {
  state: DurableObjectState;

  constructor(state: DurableObjectState) {
    this.state = state;
  }

  async fetch(request: Request): Promise<Response> {
    let value = (await this.state.storage.get<number>("count")) ?? 0;
    value++;
    await this.state.storage.put("count", value);
    return new Response(value.toString());
  }
}

Accessing from a Worker

export default {
  async fetch(request: Request, env: Env): Promise<Response> {
    const id = env.COUNTER.idFromName("my-counter");
    const stub = env.COUNTER.get(id);
    return stub.fetch(request);
  },
};

Wrangler Config

[durable_objects]
bindings = [
  { name = "COUNTER", class_name = "Counter" }
]

[[migrations]]
tag = "v1"
new_classes = ["Counter"]

Key Properties

• Single-threaded: Only one instance per ID exists globally
• Strongly consistent: All reads/writes to the same object are serialized
• Persistent storage: Key-value storage survives restarts (SQLite-backed)
• WebSocket support: Built-in WebSocket hibernation API
• Alarms: Schedule future wake-ups

Pulumi IaC

const worker = new cloudflare.WorkersScript("do-worker", {
  accountId,
  name: "do-worker",
  content: workerScript,
  module: true,
});

// Durable Object bindings are part of the Worker script resource.
// The class must be exported from the Worker module.
// Migrations are handled via wrangler.toml, not Pulumi.

Pricing

Resource	Free	Paid
Requests	1M included	$0.15/M
Duration	400K GB-s	$12.50/M GB-s
Storage reads	1M/month	$0.20/M
Storage writes	1M/month	$1.00/M
Storage	1 GB	$0.20/GB/month

References

• Durable Objects Docs
• Storage API
• WebSockets
• Alarms