API route handlers

Express, inside Next.js

Server actions serve your own forms. But sometimes you need a real HTTP endpoint: a mobile app hitting your backend, a webhook from Stripe (a URL another service calls to notify you when something happens, like a payment), a public JSON API. That is a route handler, the special file route.js:

// app/api/posts/route.js
export async function GET() {
  const posts = await db.posts.all();
  return Response.json(posts);
}

export async function POST(request) {
  const body = await request.json();
  const post = await db.posts.insert(body);
  return Response.json(post, { status: 201 });
}

This is the Backend with Node.js course condensed: GET/POST exports instead of app.get/app.post, the web-standard Request and Response objects instead of Express's req/res, and file-based paths (app/api/posts/route.js → /api/posts) instead of route strings. Even the status codes you learned (201 Created) carry straight over.

Server action or route handler?

Rule of thumb: actions are internal wiring, handlers are public doors. Actions keep the type-safe function-call feel inside your app. Handlers speak plain HTTP that anything on the internet can call, exactly like the Express APIs you built before.