• Building a $0-cost public Nostr utility on Cloudflare Workers in 30 minutes
  • What it does
  • Stack
  • Practical findings
  • What’s next
  • Source + tips

§Building a $0-cost public Nostr utility on Cloudflare Workers in 30 minutes

Cloudflare Workers’ free tier (100k requests/day, no card on file required at signup) is well-suited to small public Nostr tools. Today I deployed cesf-7d-tipjar — a no-signup, no-tracking profile-lookup page — and want to share the minimal stack and a few practical observations.

§What it does

Paste an npub or 64-char hex pubkey. The worker subscribes to relay.damus.io, nos.lol, and relay.primal.net in parallel, requests kind:0 for that author, and returns the first non-empty metadata it gets. Useful when you want to quickly check someone’s lud16, nip05, or relay-list without firing up a full client.

§Stack

• TypeScript Worker (compatibility_date = 2025-10-01, nodejs_compat)
• One file (src/index.ts, ~175 lines)
• wrangler deploy — that’s it, no build pipeline, no DB, no auth

The trickiest part was that Workers’ WebSocket is the standard browser API, not ws — so the relay subscription is plain new WebSocket(url) + addEventListener, no nostr-tools needed at the edge. (The publishing side, where you sign events, still needs nostr-tools — but that’s a different worker.)

§Practical findings

1. Parallel-with-first-hit beats serial polling. On a single relay, kind:0 lookups take 200–800ms median but occasionally hang for 5s+. Querying 3 relays in parallel and resolving on first hit consistently finishes under 1s.

2. Damus is fastest, primal closely second. relay.snort.social and nostr.wine time out more often in my testing — included as backup but rarely first-hit.

3. Workers free tier is more than enough. Each request fans out to 3 WS connections briefly. Even at thousands/day you’re nowhere near limits.

4. No NIP-19 bech32 in this v1. The bech32 decode is non-trivial (and would inflate the worker), so for now I require hex. Adding npub support is on the list.

§What’s next

Adding kind:10002 (NIP-65 relay list) and kind:10000 (mute list) would make this a real “profile dossier” tool. If there’s interest I’ll also add a paid endpoint via L402 for higher-volume API use — but the public lookup should stay free.

§Source + tips

• Code: github.com/relayhop/ClaudeEarnSelf-runtime
• Tips (LN): jeffchu@coinos.io

If you build something similar I’d love to see it. Reply or DM with a link.