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Deno KV Watch


Deno KV watch allows you to detect changes to your KV database, making it easier to build real-time applications, newsfeeds, chat, and more.

Open the default database
const kv = await Deno.openKv();
Set "counter" value to 0, then increment every second.
await kv.set(["counter"], new Deno.KvU64(0n));
setInterval(() => {
  kv.atomic().sum(["counter"], 1n).commit();
}, 1000);
Listen for changes to "counter" and log value.
for await (const [entry] of kv.watch([["counter"]])) {
  console.log(`Counter: ${entry.value}`);
You can also create a stream reader from kv.watch, which returns a ReadableStream.
const stream = kv.watch([["counter"]]).getReader();
while (true) {
  const counter = await stream.read();
  if (counter.done) {
  console.log(`Counter: ${counter.value[0].value}`);
To use server-sent events, let's create a server that responds with a stream. Each time a change to "counter" is detected, send the updated value to the client.
Deno.serve((_req) => {
  const stream = kv.watch([["counter"]]).getReader();
  const body = new ReadableStream({
    async start(controller) {
      while (true) {
        if ((await stream.read()).done) {
        const data = await kv.get(["counter"]);
          new TextEncoder().encode(`Counter: ${data.value}\n`),
    cancel() {
  return new Response(body, {
    headers: {
      "Content-Type": "text/event-stream",

Run this example locally using the Deno CLI:

deno run --unstable https://examples.deno.land/kv-watch.ts