Walk me through your hands-on experience building backend microservices and APIs in Node.js, and how you choose between Express, Fastify, and NestJS.

In Simple Words: "I am a Senior Backend and Full-Stack Engineer with extensive experience building high-throughput services using Node.js, TypeScript, and modern frameworks including Express, Fastify, and NestJS. I have architected event-driven microservices handling millions of events daily, implemented real-time bidirectional WebSocket systems with Redis Pub/Sub, designed streaming file transformation pipelines using Node.js Streams, and integrated PostgreSQL, MongoDB, and Redis data layers.

Framework selection criteria:

• Express: The battle-tested industry standard. Best when team familiarity, vast ecosystem middleware compatibility, and straightforward lightweight setups are preferred.
• Fastify: High-throughput microservices. Delivers up to 2x higher throughput than Express via compile-time JSON schema serialization (fast-json-stringify) and Radix Tree routing (find-my-way).
• NestJS: Large enterprise teams requiring an opinionated, TypeScript-first framework with built-in Dependency Injection, modular architecture, and microservice transport adapters (gRPC, RabbitMQ, Kafka)."

// Modern Fastify server setup with compile-time schema serialization:
import Fastify from 'fastify';

const server = Fastify({ logger: true });

server.get('/health', async () => ({
  status: 'ok',
  uptime: process.uptime(),
  memory: process.memoryUsage().heapUsed
}));

const start = async () => {
  await server.listen({ port: 3000, host: '0.0.0.0' });
};
start();