--- title: Use Workers KV from Durable Objects description: Read and write to/from KV within a Durable Object image: https://developers.cloudflare.com/dev-products-preview.png --- > Documentation Index > Fetch the complete documentation index at: https://developers.cloudflare.com/durable-objects/llms.txt > Use this file to discover all available pages before exploring further. [Skip to content](#%5Ftop) # Use Workers KV from Durable Objects **Last reviewed:** over 2 years ago Read and write to/from Workers KV within a Durable Object The following Worker script shows you how to configure a Durable Object to read from and/or write to a [Workers KV namespace](https://developers.cloudflare.com/kv/concepts/how-kv-works/). This is useful when using a Durable Object to coordinate between multiple clients, and allows you to serialize writes to KV and/or broadcast a single read from KV to hundreds or thousands of clients connected to a single Durable Object [using WebSockets](https://developers.cloudflare.com/durable-objects/best-practices/websockets/). Prerequisites: * A [KV namespace](https://developers.cloudflare.com/kv/api/) created via the Cloudflare dashboard or the [wrangler CLI](https://developers.cloudflare.com/workers/wrangler/install-and-update/). * A [configured binding](https://developers.cloudflare.com/kv/concepts/kv-bindings/) for the `kv_namespace` in the Cloudflare dashboard or Wrangler file. * A [Durable Object namespace binding](https://developers.cloudflare.com/workers/wrangler/configuration/#durable-objects). Configure your Wrangler file as follows: * [ wrangler.jsonc ](#tab-panel-6081) * [ wrangler.toml ](#tab-panel-6082) JSONC ``` { "$schema": "./node_modules/wrangler/config-schema.json", "name": "my-worker", "main": "src/index.ts", "kv_namespaces": [ { "binding": "YOUR_KV_NAMESPACE", "id": "" } ], "durable_objects": { "bindings": [ { "name": "YOUR_DO_CLASS", "class_name": "YourDurableObject" } ] } } ``` TOML ``` "$schema" = "./node_modules/wrangler/config-schema.json" name = "my-worker" main = "src/index.ts" [[kv_namespaces]] binding = "YOUR_KV_NAMESPACE" id = "" [[durable_objects.bindings]] name = "YOUR_DO_CLASS" class_name = "YourDurableObject" ``` * [ TypeScript ](#tab-panel-6079) * [ Python ](#tab-panel-6080) TypeScript ``` import { DurableObject } from "cloudflare:workers"; interface Env { YOUR_KV_NAMESPACE: KVNamespace; YOUR_DO_CLASS: DurableObjectNamespace; } export default { async fetch(req: Request, env: Env): Promise { // Assume each Durable Object is mapped to a roomId in a query parameter // In a production application, this will likely be a roomId defined by your application // that you validate (and/or authenticate) first. let url = new URL(req.url); let roomIdParam = url.searchParams.get("roomId"); if (roomIdParam) { // Get a stub that allows you to call that Durable Object let durableObjectStub = env.YOUR_DO_CLASS.getByName(roomIdParam); // Pass the request to that Durable Object and await the response // This invokes the constructor once on your Durable Object class (defined further down) // on the first initialization, and the fetch method on each request. // // You could pass the original Request to the Durable Object's fetch method // or a simpler URL with just the roomId. let response = await durableObjectStub.fetch(`http://do/${roomId}`); // This would return the value you read from KV *within* the Durable Object. return response; } }, }; export class YourDurableObject extends DurableObject { constructor( public state: DurableObjectState, env: Env, ) { super(state, env); } async fetch(request: Request) { // Error handling elided for brevity. // Write to KV await this.env.YOUR_KV_NAMESPACE.put("some-key"); // Fetch from KV let val = await this.env.YOUR_KV_NAMESPACE.get("some-other-key"); return Response.json(val); } } ``` Python ``` from workers import DurableObject, Response, WorkerEntrypoint from urllib.parse import urlparse, parse_qs class Default(WorkerEntrypoint): async def fetch(self, req): # Assume each Durable Object is mapped to a roomId in a query parameter # In a production application, this will likely be a roomId defined by your application # that you validate (and/or authenticate) first. url = req.url parsed_url = urlparse(url) room_id_param = parse_qs(parsed_url.query).get('roomId', [None])[0] if room_id_param: # Get a stub that allows you to call that Durable Object durable_object_stub = self.env.YOUR_DO_CLASS.getByName(room_id_param) # Pass the request to that Durable Object and await the response # This invokes the constructor once on your Durable Object class (defined further down) # on the first initialization, and the fetch method on each request. # # You could pass the original Request to the Durable Object's fetch method # or a simpler URL with just the roomId. response = await durable_object_stub.fetch(f"http://do/{room_id_param}") # This would return the value you read from KV *within* the Durable Object. return response class YourDurableObject(DurableObject): def __init__(self, state, env): super().__init__(state, env) async def fetch(self, request): # Error handling elided for brevity. # Write to KV await self.env.YOUR_KV_NAMESPACE.put("some-key", "some-value") # Fetch from KV val = await self.env.YOUR_KV_NAMESPACE.get("some-other-key") return Response.json(val) ``` ```json {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"item":{"@id":"/directory/","name":"Directory"}},{"@type":"ListItem","position":2,"item":{"@id":"/durable-objects/","name":"Durable Objects"}},{"@type":"ListItem","position":3,"item":{"@id":"/durable-objects/examples/","name":"Examples"}},{"@type":"ListItem","position":4,"item":{"@id":"/durable-objects/examples/use-kv-from-durable-objects/","name":"Use Workers KV from Durable Objects"}}]} ```