Node.js (Express, Fastify & NestJS) Backend Integration

Express.js Route Handler

Extract the visitor's real IP from x-forwarded-for or the TCP socket, and query the ParityEdge Edge API:

import express from 'express';

const app = express();
const EDGE_API_URL = 'https://api.parityedge.app/v1/lookup';
const PROJECT_ID = 'prj_live_YOUR_KEY';

app.get('/api/pricing', async (req, res) => {
  const clientIp = req.headers['x-forwarded-for'] || req.socket.remoteAddress;

  try {
    const edgeRes = await fetch(
      `${EDGE_API_URL}?projectId=${PROJECT_ID}`,
      {
        headers: {
          'x-forwarded-for': String(clientIp),
        },
      }
    );

    const parity = edgeRes.ok ? await edgeRes.json() : null;
    const basePrice = 49.00;
    const finalPrice = parity?.eligible
      ? basePrice * (1 - parity.discountPercentage / 100)
      : basePrice;

    res.json({
      basePrice,
      finalPrice,
      parity,
    });
  } catch (err) {
    res.json({ basePrice: 49.00, finalPrice: 49.00, parity: null });
  }
});

app.listen(3000, () => {
  console.log('Server listening on http://localhost:3000');
});

Fastify High-Throughput Route

In Fastify, use the native request.ip to resolve geo-located pricing in sub-10ms:

import Fastify from 'fastify';

const fastify = Fastify({ logger: true });
const EDGE_API_URL = 'https://api.parityedge.app/v1/lookup';

fastify.get('/api/pricing', async (request, reply) => {
  const clientIp = request.ip;

  const res = await fetch(`${EDGE_API_URL}?projectId=prj_live_YOUR_KEY`, {
    headers: { 'x-forwarded-for': clientIp },
  });

  const parity = res.ok ? await res.json() : null;
  return { basePrice: 49.00, parity };
});

fastify.listen({ port: 3000 });

Production Best Practices