Deno KV

What is Deno KV?

Deno KV is a key-value database built into Deno. On Deno Deploy, it's a fast, globally distributed store that requires no setup or configuration.

Quick Start

// Open the KV store (auto-connects on Deno Deploy)
const kv = await Deno.openKv();

// Store a value
await kv.set(["users", "alice"], { name: "Alice", email: "alice@example.com" });

// Retrieve a value
const result = await kv.get(["users", "alice"]);
console.log(result.value); // { name: "Alice", email: "alice@example.com" }

// Delete a value
await kv.delete(["users", "alice"]);

Keys

Keys are arrays of "key parts" that form a hierarchy:

<!-- deno-fmt-ignore -->

// Simple key
["settings"]

// Hierarchical keys
["users", "alice"]
["users", "bob"]
["posts", "2024", "01", "my-post"]

Key parts can be strings, numbers, booleans, Uint8Array, or bigints.

Basic Operations

Get

const result = await kv.get<User>(["users", "alice"]);
if (result.value) {
  console.log(result.value.name);
}

Set

await kv.set(["users", "alice"], { name: "Alice" });

// With expiration (in milliseconds)
await kv.set(["sessions", sessionId], data, { expireIn: 3600000 }); // 1 hour

Delete

await kv.delete(["users", "alice"]);

List

// List all users
const users = kv.list<User>({ prefix: ["users"] });
for await (const entry of users) {
  console.log(entry.key, entry.value);
}

// With limit
const firstTen = kv.list<User>({ prefix: ["users"] }, { limit: 10 });

Atomic Transactions

Perform multiple operations atomically (all succeed or all fail):

// Transfer credits between users
const alice = await kv.get<number>(["credits", "alice"]);
const bob = await kv.get<number>(["credits", "bob"]);

const result = await kv.atomic()
  .check(alice) // Ensure alice hasn't changed
  .check(bob) // Ensure bob hasn't changed
  .set(["credits", "alice"], alice.value! - 100)
  .set(["credits", "bob"], bob.value! + 100)
  .commit();

if (!result.ok) {
  console.log("Transaction failed - data was modified");
}

Example: Request Counter

const kv = await Deno.openKv();

Deno.serve(async () => {
  // Increment counter atomically
  const key = ["requests"];

  let result = { ok: false };
  while (!result.ok) {
    const current = await kv.get<number>(key);
    const newCount = (current.value ?? 0) + 1;

    result = await kv.atomic()
      .check(current)
      .set(key, newCount)
      .commit();
  }

  const count = (await kv.get<number>(key)).value;
  return new Response(`Requests: ${count}`);
});

Data Location

On Deno Deploy, KV data is replicated across at least three data centers in Northern Virginia (us-east-4). Cross-region replication is not currently available.

Local Development

When running locally with deno run, KV data is stored in memory by default. For persistent local storage:

// Persist to a local file
const kv = await Deno.openKv("./my-database.sqlite");

Important Notes

• Deletion is permanent - Deleting a KV instance removes all data with no recovery
• Back up important data before deleting instances
• No cross-region replication yet - data lives in us-east-4

Documentation

• Deno KV on Deploy: https://docs.deno.com/deploy/reference/deno_kv/
• Deno KV API: https://docs.deno.com/api/deno/~/Deno.Kv