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This guide walks you through a complete payment integration using a Node.js backend as an example. The same concepts apply to any programming language.

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Overview

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1. Set Up Your Server

Install the required dependencies: 
npm init -y
npm install express axios
Create your server file: 
// server.js
const express = require('express');
const crypto = require('crypto');
const axios = require('axios');

const app = express();

const KYREN_API_KEY = process.env.KYREN_API_KEY;
const KYREN_WEBHOOK_SECRET = process.env.KYREN_WEBHOOK_SECRET;
const KYREN_BASE_URL = 'https://api.kyren.top';

// Parse JSON for regular routes
app.use(express.json());

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2. Create a Product (One-Time Setup)

You only need to create a product once. You can do this via the API or the Dashboard. 
async function createProduct() {
  const response = await axios.post(`${KYREN_BASE_URL}/v1/products`, {
    name: '1000 AI Credits',
    description: 'Top up 1000 credits for AI API usage',
    price: '9.99',
    currency: 'USD',
    metadata: { credits: '1000' }
  }, {
    headers: { 'x-api-key': KYREN_API_KEY }
  });

  console.log('Product created:', response.data.data.id);
  return response.data.data;
}

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3. Create Checkout Endpoint

Add an endpoint that creates a checkout session when the customer clicks “Buy”: 
app.post('/api/buy-credits', async (req, res) => {
  try {
    const response = await axios.post(`${KYREN_BASE_URL}/v1/checkouts`, {
      productId: 'prod_abc123',  // Your product ID from step 2
      successUrl: 'https://yoursite.com/payment/success',
      cancelUrl: 'https://yoursite.com/payment/cancel',
      customerEmail: req.body.email,
      metadata: {
        userId: req.body.userId
      }
    }, {
      headers: { 'x-api-key': KYREN_API_KEY }
    });

    // Return the checkout URL to the frontend
    res.json({ checkoutUrl: response.data.data.url });
  } catch (error) {
    console.error('Checkout creation failed:', error.response?.data);
    res.status(500).json({ error: 'Failed to create checkout' });
  }
});

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4. Handle the Frontend Redirect

On your frontend, redirect the customer to the checkout page: 
<button id="buy-btn">Buy 1000 Credits - $9.99</button>

<script>
document.getElementById('buy-btn').addEventListener('click', async () => {
  const response = await fetch('/api/buy-credits', {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify({
      email: 'customer@example.com',
      userId: 'user_123'
    })
  });

  const { checkoutUrl } = await response.json();
  window.location.href = checkoutUrl;
});
</script>

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5. Handle Webhooks

Add a webhook endpoint to receive payment notifications: 
function verifySignature(payload, signature, timestamp) {
  const data = `${timestamp}.${payload}`;
  const expected = 'sha256=' + crypto
    .createHmac('sha256', KYREN_WEBHOOK_SECRET)
    .update(data)
    .digest('hex');

  // Verify timestamp is within 5 minutes
  const currentTime = Math.floor(Date.now() / 1000);
  if (Math.abs(currentTime - parseInt(timestamp)) > 300) {
    return false;
  }

  return crypto.timingSafeEqual(
    Buffer.from(expected),
    Buffer.from(signature)
  );
}

app.post('/webhooks/kyren',
  express.raw({ type: 'application/json' }),
  (req, res) => {
    const signature = req.headers['x-kyren-signature'];
    const timestamp = req.headers['x-kyren-timestamp'];
    const payload = req.body.toString();

    if (!verifySignature(payload, signature, timestamp)) {
      return res.status(400).send('Invalid signature');
    }

    const event = JSON.parse(payload);

    switch (event.type) {
      case 'order.paid':
        const { order_id, product_id, customer_email, amount, currency } = event.data;
        console.log(`Payment received: ${amount} ${currency} from ${customer_email}`);
        // TODO: Fulfill the order — add credits to the user's account
        break;
      default:
        console.log(`Unhandled event type: ${event.type}`);
    }

    res.status(200).send('OK');
  }
);

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6. Start the Server

app.listen(3000, () => {
  console.log('Server running on http://localhost:3000');
});
Run your server: 
KYREN_API_KEY=kyren_test_xxx KYREN_WEBHOOK_SECRET=whsec_xxx node server.js

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7. Test the Flow

  1. Open your app and click “Buy 1000 Credits”
  2. You’ll be redirected to the Kyren Pay checkout page
  3. Enter test card number 4242 4242 4242 4242
  4. Complete the payment
  5. Check your server logs — you should see the webhook arrive
Congratulations! You’ve successfully integrated Kyren Pay. When you’re ready, switch to your live API key and start accepting real payments.

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Next Steps

Webhook Events

See all available webhook event types

Code Examples

See integration examples in other languages