How I built a QR code redirect system with Cloudflare Workers for sub-100ms response time

#architecture #performance #serverless #showdev

I'm building a one-time payment QR code service, and one of the most critical pieces is the redirect system. When someone scans a QR code, the redirect needs to be instant — any delay and people think the code is broken.

Here's how I architected it.

The Problem

Most QR code services run redirects through their main app server. That means:

Cold starts on serverless (500ms+)
Single region latency
Database queries on every scan

For a QR code that might be printed on a restaurant menu and scanned 100 times a day, that's unacceptable.

The Solution: Cloudflare Workers

Cloudflare Workers run at the edge in 300+ cities worldwide. Every scan hits the nearest edge node.

The flow:

User scans QR → hits ownqrcode.com/r/{slug}
Cloudflare Worker intercepts the request
Worker looks up the destination URL from Supabase
302 redirect to destination
Async: log scan event (device, location from request.cf)

Key decisions

302 not 301: We use 302 (temporary) redirects because users can change their destination URL anytime. A 301 would get cached by browsers and CDNs, making URL changes invisible to returning visitors.

Geo data for free: Cloudflare's request.cf object gives us city, country, latitude, and longitude on every request — no external geo API needed. This powers our scan analytics dashboard.

Async logging: We don't await the Supabase insert for scan events. The redirect fires immediately, and the analytics data gets logged in the background using ctx.waitUntil(). Users get their redirect in <50ms.

Results

Average redirect time: ~40ms
Works globally with no cold starts
Scan analytics with device + location data at zero extra cost
Total infra cost: ~$5/month on Cloudflare Workers

Stack

Redirect service: Cloudflare Workers
Main app: Next.js 14 (App Router) on Vercel
Database: Supabase (PostgreSQL)
Payments: Stripe (one-time, no subscriptions)

If you're building anything that needs fast redirects at scale, Cloudflare Workers is hard to beat.

I'm building OwnQR — a $15 one-time QR code generator for small businesses. Happy to answer questions about the architecture.

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