Node.js Writing Code

Quick reference for writing production-quality Node.js backend services. Each section summarizes the key rules — reference files provide full examples and edge cases.

API Architecture (Fastify)

Plugin-Based Design

Everything in Fastify is a plugin — routes, middleware, database connections, services.

// Register plugins in order
await app.register(cors, { origin: ["http://localhost:3000"], credentials: true });
await app.register(jwt, { secret: process.env.JWT_SECRET! });

// Route plugins with prefix
await app.register(authRoutes, { prefix: "/auth" });
await app.register(userRoutes, { prefix: "/users" });