Connect to Redis

Overview

Redis in Cosmoner runs Valkey — the Linux Foundation's BSD-licensed fork of Redis 7.2, compatible with it command for command. Any Redis client library connects to it unchanged: use it for caching, sessions, rate limiting, queues and pub/sub as you would Redis.

Every database runs on Cosmoner's own hardware in Stockholm, so its data stays in Sweden. Connections are TLS-only and need a password.

Plans and prices are on Valkey & Redis Pricing.

Create a database

In your project, go to Redis and create a database. You choose:

• Plan — how much data it holds. Plans differ in dataset size, not in speed: a single instance runs commands on one thread whichever plan it is on.
• Persistence — how much of the data survives a restart. See Choosing persistence.

When it is ready, its page shows the host, port, password and a ready-made Connection string.

Connect

The connection string looks like this:

rediss://:<password>@valkey-<id>.valkey.cosmoner.com:6379

Note the scheme: rediss://, with two s. TLS is required, and a client given redis:// tries a plaintext connection that is refused.

From your app

Store the connection string as a secret — it contains the password — and link it to your app as an environment variable, e.g. REDIS_URL, with Link secret. Then redeploy the app so it picks the variable up.

Node.js, with redis:

import { createClient } from "redis";

const client = createClient({ url: process.env.REDIS_URL });
client.on("error", (err) => console.error("Redis error", err));
await client.connect();

await client.set("greeting", "hej", { EX: 60 });

Node.js, with ioredis:

import Redis from "ioredis";

const redis = new Redis(process.env.REDIS_URL);

Python, with redis:

import os
import redis

r = redis.Redis.from_url(os.environ["REDIS_URL"])
r.set("greeting", "hej", ex=60)

PHP, with Predis:

$client = new Predis\Client(getenv('REDIS_URL'));
$client->set('greeting', 'hej');

All of these read the rediss:// scheme and turn TLS on themselves.

From your machine

The host is reachable from anywhere, so you can inspect a database with redis-cli or a GUI client:

redis-cli --tls -u "rediss://:<password>@valkey-<id>.valkey.cosmoner.com:6379"

Treat the password like any other credential: it is the only thing between the internet and your data.

Choosing persistence

Persistence is included in every plan, and the mode never changes the price.

When it is full

A plan's dataset size is its memory limit. When the data reaches it, Valkey makes room by evicting the least recently used keys — any key, whether or not it has an expiry. Writes keep succeeding; old data goes.

That is what you want from a cache, and a surprise anywhere else. If you keep data that must not disappear, such as a job queue, size the plan for it and watch its usage, or keep that data in a database instead.

Limits

• No high availability. A database is a single instance with no automatic failover. Plan for it being briefly unreachable during maintenance, and make your app treat a cache miss or a connection error as recoverable.
• One region: Stockholm, Sweden.

Troubleshooting

Connection refused or reset immediately. The URL uses redis://. Change it to rediss://.

WRONGPASS or NOAUTH. The password in the URL is wrong or missing — copy the connection string from the database's page again.

Keys disappear without expiring. The dataset reached the plan's size and the least recently used keys were evicted. Move to a larger plan, or set expiries so the data you keep is the data you use.