FastAPI vs Express.js Comparison

# FastAPI - User CRUD API
from fastapi import FastAPI, HTTPException
from pydantic import BaseModel, EmailStr

app = FastAPI(title="User API")

class UserCreate(BaseModel):
    name: str
    email: EmailStr
    age: int

class UserResponse(UserCreate):
    id: int

users_db: dict[int, UserResponse] = {}

@app.post("/users", response_model=UserResponse, status_code=201)
async def create_user(user: UserCreate):
    user_id = len(users_db) + 1
    db_user = UserResponse(id=user_id, **user.model_dump())
    users_db[user_id] = db_user
    return db_user

@app.get("/users/{user_id}", response_model=UserResponse)
async def get_user(user_id: int):
    if user_id not in users_db:
        raise HTTPException(status_code=404, detail="User not found")
    return users_db[user_id]

// Express.js - User CRUD API (TypeScript)
import express, { Request, Response } from 'express';

const app = express();
app.use(express.json());

interface User {
  id: number;
  name: string;
  email: string;
  age: number;
}

const usersDb: Map<number, User> = new Map();
let nextId = 1;

app.post('/users', (req: Request, res: Response) => {
  const { name, email, age } = req.body;
  if (!name || !email || !age) {
    return res.status(400).json({ error: 'Missing field' });
  }
  const user: User = { id: nextId++, name, email, age };
  usersDb.set(user.id, user);
  res.status(201).json(user);
});

app.get('/users/:id', (req: Request, res: Response) => {
  const user = usersDb.get(Number(req.params.id));
  if (!user) return res.status(404).json({ error: 'Not found' });
  res.json(user);
});

app.listen(3000);