2x lazymac

Posted on Apr 10

Building APIs on Cloudflare Workers: Zero to Production in 1 Hour

#api #webdev #cloudflare #tutorial

Cloudflare Workers let you deploy serverless APIs globally in seconds. No Docker, no Kubernetes, no cold starts. Here is how to go from zero to a production API in under an hour.

Why Cloudflare Workers?

0ms cold starts — V8 isolates, not containers
Global by default — runs in 300+ edge locations
Free tier — 100K requests/day
Simple deployment — wrangler deploy and done

Setup (5 Minutes)

# Install Wrangler CLI
npm install -g wrangler

# Login to Cloudflare
wrangler login

# Create a new project
wrangler init my-api
cd my-api

Build a REST API (20 Minutes)

// src/index.js
export default {
  async fetch(request, env) {
    const url = new URL(request.url);
    const path = url.pathname;

    // CORS headers
    const corsHeaders = {
      'Access-Control-Allow-Origin': '*',
      'Content-Type': 'application/json'
    };

    if (request.method === 'OPTIONS') {
      return new Response(null, { headers: corsHeaders });
    }

    // Routes
    if (path === '/api/health') {
      return Response.json({ status: 'ok', region: request.cf?.colo }, { headers: corsHeaders });
    }

    if (path === '/api/data') {
      const data = await env.MY_KV.get('cached-data', 'json');
      return Response.json({ data }, { headers: corsHeaders });
    }

    if (path === '/api/process' && request.method === 'POST') {
      const body = await request.json();
      const result = processData(body);
      return Response.json(result, { headers: corsHeaders });
    }

    return Response.json({ error: 'Not found' }, { status: 404, headers: corsHeaders });
  }
};

function processData(input) {
  return {
    processed: true,
    timestamp: new Date().toISOString(),
    input_size: JSON.stringify(input).length
  };
}

Add KV Storage (10 Minutes)

# Create a KV namespace
wrangler kv:namespace create MY_KV

# Add to wrangler.toml
# [[kv_namespaces]]
# binding = "MY_KV"
# id = "your-namespace-id"

// Write and read from KV
await env.MY_KV.put('key', JSON.stringify({ value: 42 }));
const data = await env.MY_KV.get('key', 'json');

Deploy (2 Minutes)

# Deploy to production
wrangler deploy

# Your API is live at: https://my-api.your-subdomain.workers.dev

Add a Custom Domain (5 Minutes)

# In wrangler.toml
# routes = [
#   { pattern = "api.yourdomain.com/*", zone_name = "yourdomain.com" }
# ]

wrangler deploy

Production Patterns

Rate Limiting

async function rateLimit(request, env) {
  const ip = request.headers.get('CF-Connecting-IP');
  const key = `rate:${ip}`;
  const count = parseInt(await env.MY_KV.get(key) || '0');

  if (count > 100) {
    return Response.json({ error: 'Rate limited' }, { status: 429 });
  }

  await env.MY_KV.put(key, String(count + 1), { expirationTtl: 3600 });
  return null; // Continue processing
}

Error Handling

try {
  const result = await processRequest(request);
  return Response.json(result);
} catch (err) {
  return Response.json(
    { error: 'Internal error', message: err.message },
    { status: 500 }
  );
}

Real Example: AI Spend Tracker

We built the AI Spend API entirely on Cloudflare Workers. It handles thousands of requests daily with sub-50ms latency globally.

# Try it
curl "https://api.lazy-mac.com/ai-spend/calculate?model=gpt-4&input_tokens=1000&output_tokens=500"

The entire stack: Workers + KV + D1 (SQLite). No servers to manage.

Get the AI FinOps API | Build your own APIs

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