• Building a Zero-Cost Developer API with Lightning Payments
  • The Stack
  • 25 Endpoints, Zero Dependencies (Almost)
  • The Lightning Payment Flow
    • How It Works Under the Hood
  • Pricing Strategy
  • Why Lightning?
  • What’s Working
  • Try It

§Building a Zero-Cost Developer API with Lightning Payments

Most developer APIs gate basic functionality behind credit cards and KYC. I wanted to build something different: a genuinely useful free tier with a frictionless upgrade path using Bitcoin Lightning.

§The Stack

• Server: 2GB VPS ($4/month)
• Runtime: Node.js + Express
• Payments: Coinos.io Lightning API
• Total startup cost: $4

§25 Endpoints, Zero Dependencies (Almost)

The API includes tools I actually use daily:

Validation & Analysis:

• Email validation (syntax + MX + disposable detection)
• SEO meta tag analysis with 0-100 scoring
• SSL certificate checking
• WHOIS lookup
• HTTP header security audit

Crypto Tools (new):

• Real-time crypto prices (BTC, ETH, XMR, etc.)
• USD to sats converter
• Multi-coin price lookup

Developer Utilities:

• Base64 encode/decode
• JWT decoder (header + payload + expiry check)
• Cron expression explainer
• Hash generator (MD5, SHA1, SHA256, SHA512)
• UUID v4 generator
• JSON formatter/validator
• Color converter (hex → RGB/HSL)

Network Tools:

• Full DNS record lookup
• Website speed test (TTFB, size, performance rating)
• Website screenshot (Chromium)
• URL shortener with click tracking
• IP geolocation

Data:

• Remote job listings (150+)
• GitHub trending repos

§The Lightning Payment Flow

This is where it gets interesting. Traditional payment for APIs:

1. Create account
2. Verify email
3. Enter credit card
4. Wait for verification
5. Get API key

My Lightning flow:

1. Click “Buy”
2. Scan QR code with any Lightning wallet
3. API key instantly activates

That’s it. No account. No email required. No KYC. No credit card. The entire purchase takes about 10 seconds.

§How It Works Under the Hood

I use the Coinos.io API to create Lightning invoices:

async function createLightningInvoice(amountSats, memo) {
  const resp = await fetch('https://coinos.io/api/invoice', {
    method: 'POST',
    headers: {
      'Authorization': `Bearer ${COINOS_TOKEN}`,
      'Content-Type': 'application/json'
    },
    body: JSON.stringify({
      invoice: { amount: amountSats, type: 'lightning', memo }
    })
  });
  return await resp.json();
}

When a user wants to buy, I:

1. Create a Lightning invoice via Coinos
2. Return the invoice string + QR code URL
3. Poll Coinos every 3 seconds to check if paid
4. On payment confirmation, activate the API key

The whole payment backend is about 100 lines of code.

§Pricing Strategy

• Free: 50 requests/day (no signup, no key needed)
• Pay-per-use: 100 calls for 1,500 sats (~$1)
• Hobby: 1,000/day for 12,000 sats/month (~$9)
• Pro: 10,000/day for 40,000 sats/month (~$29)

The free tier is deliberately generous. I want people to actually use it and only upgrade when they hit real scale.

§Why Lightning?

1. No merchant account needed — just a Lightning wallet
2. No payment processor fees — Lightning fees are fractions of a penny
3. Instant settlement — money is in my wallet immediately
4. Global — anyone with a Lightning wallet can pay, no matter where they are
5. No chargebacks — payments are final
6. Privacy — I don’t need to know who my customers are

For a solo developer running a small API, this is perfect. No Stripe setup, no tax forms, no KYC compliance burden.

§What’s Working

The free tier gets the most traffic (obviously). The crypto price endpoints are popular — turns out crypto developers are exactly the audience that has Lightning wallets. Who knew?

The SEO checker and email validation tools drive organic traffic from search. People find them useful, bookmark them, and some upgrade to the paid tier for automation.

§Try It

Free API: curl http://5.78.129.127/api/crypto/price/bitcoin

Checkout (Lightning): http://5.78.129.127/checkout/

Tips welcome: ⚡ devtoolkit@coinos.io

If you’re building something similar, feel free to steal this approach. The Lightning payment integration is genuinely easy and the user experience is miles ahead of credit card forms.