Why Deno KV Could Be Your Next Strongly Consistent Key‑Value Database

Deno KV is a newly announced, strongly consistent key‑value database from the Deno team, replicated across 35 global regions to provide low‑latency reads.

Key features include:

Local or hosted operation : Run locally backed by SQLite for development and testing, or deploy as a zero‑configuration hosted service powered by FoundationDB.

Simple yet powerful : Stores any serializable JavaScript value such as objects, arrays, BigInts, dates, etc.

Basic usage example:

const kv = await Deno.openKv();
const key = ["users", crypto.randomUUID()];
const value = { name: "Alice", created: new Date() };
await kv.set(key, value);
const result = await kv.get(key);
console.log(result.value); // { name: "Alice", created: 2023-05-01T09:24:07.620Z }

Listing keys with a prefix:

await kv.set(["users", "alice"], { birthday: "January 1, 1990" });
await kv.set(["users", "sam"], { birthday: "February 14, 1985" });
await kv.set(["users", "taylor"], { birthday: "December 25, 1970" });
const iter = kv.list({ prefix: ["users"] });
for await (const entry of iter) {
  console.log(entry.key);
  console.log(entry.value);
}

Atomic transactions are created with kv.atomic(), allowing strong consistency across multiple keys:

const kv = await Deno.openKv();
const change = 10;
const bob = await kv.get(["balance", "bob"]);
const liz = await kv.get(["balance", "liz"]);
if (liz.value < change) { throw "not enough balance"; }
const success = await kv.atomic()
  .check(bob, liz)
  .set(["balance", "bob"], bob.value - change)
  .set(["balance", "liz"], liz.value + change)
  .commit();

Deno KV supports two consistency models: serializability (the highest isolation level) and linearizability (immediate visibility of writes). Reads can be performed with eventual or strong consistency:

// Eventual consistency read
await db.get(["my-key"], { consistency: "eventual" });
// Strong consistency read
await db.get(["my-key"], { consistency: "strong" });

Example of a globally consistent counter using Deno Deploy:

import { serve } from "/[email protected]/http/server.ts";
const db = await Deno.openKv();
serve(async (req) => {
  await db.atomic().sum(["views"], 1n).commit();
  const res = await db.get(["views"]);
  const views = res.value.value;
  return new Response(`Views: ${views}`);
});

To try Deno KV, developers must join the waitlist at https://deno.com/kv.