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miccho27
miccho27

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I Built 25 Cloudflare Workers APIs — Here's What I Learned

#cloudflare #api #webdev #javascript

Over the past few months, I built and deployed 25 APIs on Cloudflare Workers. All running on the free tier. Total monthly hosting cost: $0.

Here's what I learned about building, deploying, and monetizing utility APIs at scale.

The Stack

Every API follows the same pattern:

worker-api/
├── src/
│   └── index.js      # Single entry point
├── wrangler.toml      # Cloudflare config
└── package.json
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No frameworks. No bundlers. Just vanilla JavaScript on Cloudflare Workers.

The 25 APIs

Here's a sampling of what I built:

API Purpose Complexity
Readability Score Text analysis (Flesch-Kincaid, SMOG, ARI) Medium
QR Code Generator Generate QR codes from text/URL Low
Password Generator Cryptographically secure passwords Low
Markdown to HTML CommonMark-compliant conversion Medium
Color Converter HEX/RGB/HSL conversion Low
Base64 Encoder Encode/decode Base64 Low
JSON Formatter Pretty-print & validate JSON Low
URL Shortener Create short URLs Medium
Hash Generator MD5, SHA-1, SHA-256, SHA-512 Low
Timezone Converter Convert between timezones Medium
Email Validator Syntax + MX record validation Medium
IP Geolocation IP to country/city lookup Medium
Currency Exchange Real-time exchange rates High
Text Summarizer Extractive summarization High
SEO Analyzer On-page SEO scoring High

All listed on RapidAPI.

5 Lessons Learned

1. One endpoint is better than ten

My most-used APIs have one endpoint. Send data, get results. No complex auth flows, no pagination, no state management.

export default {
  async fetch(request) {
    const { text } = await request.json();
    const result = analyze(text);
    return Response.json(result);
  }
};
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2. The free tier is generous (but has gotchas)

Cloudflare Workers free tier:

  • ✅ 100,000 requests/day
  • ✅ 10ms CPU time per request
  • ❌ No KV storage (need paid plan)
  • ❌ No Durable Objects

For stateless computation APIs, the free tier is perfect. For anything needing storage, you'll hit limits fast.

3. Error handling is 80% of the code

The actual logic for most APIs is 20-30 lines. Input validation, error messages, edge cases, and CORS handling make up the rest.

// Validation pattern I use everywhere
if (!text || typeof text !== 'string') {
  return Response.json(
    { error: 'Missing required field: text' },
    { status: 400 }
  );
}
if (text.length > 10000) {
  return Response.json(
    { error: 'Text exceeds 10,000 character limit' },
    { status: 413 }
  );
}
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4. Documentation sells APIs

The APIs with the most subscribers on RapidAPI aren't the most complex — they're the best documented. Clear examples, realistic response samples, and a "try it" button.

5. Bundle related APIs, don't build monoliths

I started with a "Swiss Army Knife API" that did everything. Nobody used it. When I split it into focused, single-purpose APIs, subscriptions went up.

Deployment Workflow 

# Deploy all 25 APIs
for dir in workers/*/; do
  cd "$dir"
  wrangler deploy
  cd ..
done
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Each API deploys in under 5 seconds. Total deployment time for all 25: ~2 minutes.

What's Next

I'm expanding to 30+ APIs by Q2 2026. The pattern is proven — the marginal cost of adding a new API is near zero.

If you're looking for utility APIs, check them out on RapidAPI.

What APIs have you built on Cloudflare Workers? I'd love to hear about your experience with the platform.

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