Set up @upstash/redis in a Cloudflare Workers or Vercel Edge runtime and avoid connection pitfalls

Documented steps

1. Install the SDK: npm install @upstash/redis.
2. Create a database in the Upstash console and copy UPSTASH_REDIS_REST_URL and UPSTASH_REDIS_REST_TOKEN.
3. Vercel Edge / Node.js: import { Redis } from '@upstash/redis'; const redis = Redis.fromEnv() — it reads both env vars from process.env.
4. Cloudflare Workers, service-worker syntax: import { Redis } from '@upstash/redis/cloudflare'; const redis = Redis.fromEnv().
5. Cloudflare Workers, module syntax: pass env explicitly — export default { async fetch(request, env) { const redis = Redis.fromEnv(env); ... } }.
6. Set both credentials as Worker secrets/vars (wrangler secret put UPSTASH_REDIS_REST_URL / UPSTASH_REDIS_REST_TOKEN, or via the dashboard) rather than assuming process.env access.
7. Fastly Compute: import { Redis } from '@upstash/redis/fastly' and construct new Redis({ url, token, backend: <BACKEND_NAME> }) where BACKEND_NAME matches a backend in fastly.toml.
8. Deno Deploy / Netlify Edge: import { Redis } from 'https://deno.land/x/upstash_redis/mod.ts'; const redis = Redis.fromEnv().
9. Understand why REST is required: edge/serverless runtimes restrict raw TCP sockets, so the client speaks HTTP(S)/fetch to the REST API rather than opening a Redis TCP connection the way ioredis or node-redis would.
10. Rely on the default auto-pipelining and batch calls with Promise.all instead of awaiting each command, reducing concurrent outbound fetches — useful since Cloudflare Workers caps simultaneous requests at 6.
11. Customize retries at construction time if needed: new Redis({ url, token, retry: { retries: 5, backoff: (retryCount) => Math.exp(retryCount) * 50 } }).
12. On Node.js v17 and earlier, import '@upstash/redis/with-fetch' since native fetch is unavailable there.
13. For lower edge read latency consider a Global Database: one primary region for writes plus read regions near your functions.
14. Official docs: https://upstash.com/docs/redis/sdks/ts/getstarted | https://upstash.com/docs/redis/sdks/ts/deployment | https://upstash.com/docs/redis/features/globaldatabase | https://upstash.com/docs/redis/sdks/ts/retries