Deno KV: Key/Value Database

Deno KV is a key/value database built in to the Deno runtime, and works with zero configuration on Deno Deploy. It's great for use cases that require fast reads and don't require the query flexibility of a SQL database.

Open the default database

const kv = await Deno.openKv();

Define an interface in TypeScript for our data

enum Rank {
  Bronze,
  Silver,
  Gold,
}

interface Player {
  username: string;
  rank: Rank;
}

Create a few instances for testing

const player1: Player = { username: "carlos", rank: Rank.Bronze };
const player2: Player = { username: "briana", rank: Rank.Silver };
const player3: Player = { username: "alice", rank: Rank.Bronze };

Store object data in Deno KV using the "set" operation. Keys can be arranged hierarchically, not unlike resources in a REST API.

await kv.set(["players", player1.username], player1);
await kv.set(["players", player2.username], player2);
await kv.set(["players", player3.username], player3);

The "set" operation is used to both create and update data for a given key

player3.rank = Rank.Gold;
await kv.set(["players", player3.username], player3);

Fetch a single object by key with the "get" operation

const record = await kv.get(["players", "alice"]);
const alice: Player = record.value as Player;
console.log(record.key, record.versionstamp, alice);

Fetch several objects by key with "getMany"

const [record1, record2] = await kv.getMany([
  ["players", "carlos"],
  ["players", "briana"],
]);
console.log(record1, record2);

List several records by key prefix - note that results are ordered lexicographically, so our players will be fetched in the order "alice", "briana", "carlos"

const records = kv.list({ prefix: ["players"] });
const players = [];
for await (const res of records) {
  players.push(res.value as Player);
}
console.log(players);

Delete a value for a given key

await kv.delete(["players", "carlos"]);

The Deno.KvU64 object is a wrapper for 64 bit integers (BigInt), so you can quickly update very large numbers. Let's add a "score" for alice.

const aliceScoreKey = ["scores", "alice"];
await kv.set(aliceScoreKey, new Deno.KvU64(0n));

Add 10 to the player's score in an atomic transaction

await kv.atomic()
  .mutate({
    type: "sum",
    key: aliceScoreKey,
    value: new Deno.KvU64(10n),
  })
  .commit();
const newScore = (await kv.get<Deno.KvU64>(aliceScoreKey)).value;
console.log("Alice's new score is: ", newScore);

Run this example locally using the Deno CLI:

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

Additional resources:

Connect to Postgres Deno KV Watch