Setup & Installation

mkdir backend-api && cd backend-api
pnpm init
pnpm add express cors helmet express-rate-limit zod
pnpm add -D typescript tsx @types/express @types/node
npx tsc --init

// src/server.ts
import { createApp } from "./app";
 
const PORT = process.env.PORT ?? 4000;
 
const app = createApp();
 
app.listen(PORT, () => {
  console.log(`API running on http://localhost:${PORT}`);
});

// src/app.ts
import express from "express";
import helmet from "helmet";
import cors from "cors";
import { healthRouter } from "./routes/health.routes";
import { v1Router } from "./routes/v1";
import { errorHandler } from "./middleware/error.middleware";
 
export function createApp() {
  const app = express();
 
  app.use(helmet());
  app.use(cors({ origin: process.env.CORS_ORIGIN?.split(",") }));
  app.use(express.json());
 
  app.use("/health", healthRouter);
  app.use("/v1", v1Router);
 
  app.use(errorHandler);
  return app;
}

cp .env.example .env.local

NODE_ENV=development
PORT=4000
CORS_ORIGIN=http://localhost:3000
 
# Cognito
COGNITO_USER_POOL_ID=us-east-1_xxxxx
COGNITO_REGION=us-east-1
COGNITO_CLIENT_ID=xxxxxxxx
 
# PostgreSQL (Sequelize or Drizzle)
DATABASE_URL=postgres://user:password@localhost:5432/app
 
# MongoDB
MONGODB_URI=mongodb://localhost:27017/app
 
# Supabase
SUPABASE_URL=https://xxxx.supabase.co
SUPABASE_SERVICE_ROLE_KEY=eyJ...   # Server only — never expose to client

docker compose up -d postgres mongo
docker compose ps

# docker-compose.yml
services:
  postgres:
    image: postgres:16-alpine
    ports: ["5432:5432"]
    environment:
      POSTGRES_USER: user
      POSTGRES_PASSWORD: password
      POSTGRES_DB: app
  mongo:
    image: mongo:7
    ports: ["27017:27017"]

{
  "scripts": {
    "dev": "tsx watch src/server.ts",
    "build": "tsc",
    "start": "node dist/server.js",
    "lint": "eslint src/",
    "typecheck": "tsc --noEmit",
    "test": "vitest run"
  }
}

pnpm dev
curl http://localhost:4000/health
# {"status":"ok","service":"backend-api"}