Build a game backend with Valkey in Node.js

mkdir valkey-arcade && cd valkey-arcadenpm init -ynpm install iovalkey

export VALKEY_URL='rediss://default:<password>@inst-<id>.eu.kvnest.com:6380'

import Valkey from "iovalkey"; const client = new Valkey(process.env.VALKEY_URL); console.log(await client.ping()); // PONG // How long does a round trip from your machine take?const start = performance.now();for (let i = 0; i < 100; i++) await client.ping();console.log(`Average round trip: ${((performance.now() - start) / 100).toFixed(2)} ms`); await client.quit();

node level-1.mjs

import Valkey from "iovalkey"; const client = new Valkey(process.env.VALKEY_URL); // A save slot: a key holds any string, JSON included.await client.set("save:ada", JSON.stringify({ level: 3, lives: 2 }));console.log(JSON.parse(await client.get("save:ada"))); // A shield power-up that wears off by itself after 5 seconds.await client.set("powerup:ada:shield", "on", "EX", 5);console.log("Shield TTL:", await client.ttl("powerup:ada:shield"), "seconds"); await new Promise((resolve) => setTimeout(resolve, 6000));console.log("Shield after 6 seconds:", await client.get("powerup:ada:shield")); // null await client.quit();

node level-2.mjs

import Valkey from "iovalkey"; const client = new Valkey(process.env.VALKEY_URL); // Stands in for a slow database query or API call.async function loadProfileFromDatabase(id) {  await new Promise((resolve) => setTimeout(resolve, 300));  return { id, name: "Ada", favouriteGame: "Nest Invaders" };} // Cache-aside: ask Valkey first; on a miss, load and keep it for 60 seconds.async function getProfile(id) {  const key = `cache:profile:${id}`;  const cached = await client.get(key);  if (cached) return JSON.parse(cached);   const profile = await loadProfileFromDatabase(id);  await client.set(key, JSON.stringify(profile), "EX", 60);  return profile;} await client.del("cache:profile:ada"); // start with a cold cachefor (const call of ["1st", "2nd", "3rd"]) {  const start = performance.now();  await getProfile("ada");  console.log(`${call} call: ${(performance.now() - start).toFixed(1)} ms`);} await client.quit();

node level-3.mjs

import Valkey from "iovalkey"; const client = new Valkey(process.env.VALKEY_URL); // 1,000 players finish a game at the same moment.await Promise.all(Array.from({ length: 1000 }, () => client.incr("stats:games_played")));console.log("Games played:", await client.get("stats:games_played")); // Coins go up and down by any amount.await client.incrby("coins:ada", 50);await client.decrby("coins:ada", 20);console.log("Ada's coins:", await client.get("coins:ada")); await client.quit();

node level-4.mjs

import Valkey from "iovalkey"; const client = new Valkey(process.env.VALKEY_URL); await client.zadd("leaderboard", 4200, "ada", 3100, "linus", 5600, "grace"); // GT: a score only replaces a lower personal best.await client.zadd("leaderboard", "GT", 6100, "ada");await client.zadd("leaderboard", "GT", 1000, "grace"); // ignored, 5600 is higher // The top 3, highest first, with their scores.const top = await client.zrange("leaderboard", 0, 2, "REV", "WITHSCORES");for (let i = 0; i < top.length; i += 2) console.log(`${i / 2 + 1}. ${top[i]} ${top[i + 1]}`); // Ranks start at 0, so add 1 for humans.const rank = await client.zrevrank("leaderboard", "linus");console.log(`Linus is #${rank + 1}`); await client.quit();

node level-5.mjs

import Valkey from "iovalkey"; const client = new Valkey(process.env.VALKEY_URL); // One key per player, one field per attribute.await client.hset("player:ada", { name: "Ada", country: "DE", level: 1, coins: 30 }); // Change single fields without reading the rest.await client.hincrby("player:ada", "level", 1); // level up!await client.hset("player:ada", "title", "Cache Cadet"); console.log(await client.hgetall("player:ada"));console.log("Level:", await client.hget("player:ada", "level")); await client.quit();

node level-6.mjs

import Valkey from "iovalkey"; const client = new Valkey(process.env.VALKEY_URL); // At most 5 score submissions per player in each 10-second window.async function allowSubmit(player) {  const key = `ratelimit:${player}`;  // MULTI/EXEC runs both commands as one unit. NX sets the expiry only if  // there is none yet, so the window starts at the first submission.  const [[, count]] = await client.multi().incr(key).expire(key, 10, "NX").exec();  return count <= 5;} for (let i = 1; i <= 7; i++) {  const ok = await allowSubmit("mallory");  console.log(`Submission ${i}: ${ok ? "accepted" : "slow down!"}`);} await client.quit();

node level-7.mjs

import Valkey from "iovalkey"; const client = new Valkey(process.env.VALKEY_URL);// A subscribed connection can only listen, so the feed gets its own.const feed = client.duplicate(); feed.on("message", (channel, message) => console.log(`📣 [${channel}] ${message}`));await feed.subscribe("arcade:events"); const listeners = await client.publish("arcade:events", "ada set a new high score: 6100");await client.publish("arcade:events", "grace joined the game");console.log(`Delivered to ${listeners} listener(s)`); // Give the messages a moment to arrive, then hang up.await new Promise((resolve) => setTimeout(resolve, 500));await feed.quit();await client.quit();

node level-8.mjs

import Valkey from "iovalkey"; const client = new Valkey(process.env.VALKEY_URL);const feed = client.duplicate();feed.on("message", (channel, message) => console.log(`  📣 ${message}`));await feed.subscribe("arcade:events"); // Every level so far, in one function.async function submitScore(player, score) {  const limitKey = `ratelimit:${player}`;  const [[, attempts]] = await client.multi().incr(limitKey).expire(limitKey, 10, "NX").exec();  if (attempts > 5) return `${player}: rejected, too many submissions`;   await client.hincrby(`player:${player}`, "games", 1);  // CH makes ZADD count changed scores, so 1 means a new personal best.  const improved = await client.zadd("leaderboard", "GT", "CH", score, player);  if (improved) await client.publish("arcade:events", `${player} reached ${score}`);  return `${player}: ${score}${improved ? " (new best!)" : ""}`;} const games = [["ada", 7300], ["grace", 6800], ["ada", 6900], ["grace", 7600]];for (const [player, score] of games) console.log(await submitScore(player, score)); // Mallory spams submissions, hoping a lucky one sticks.for (let i = 1; i <= 7; i++) console.log(await submitScore("mallory", 5000 + i * 100)); const top = await client.zrange("leaderboard", 0, 2, "REV", "WITHSCORES");console.log("\n🏆 Top 3");for (let i = 0; i < top.length; i += 2) console.log(`${i / 2 + 1}. ${top[i]} ${top[i + 1]}`); await feed.quit();await client.quit();

node level-9.mjs