VibeFast

Is NextJS Backend or Frontend?

It's both. Next.js blurs the line with Server Actions. See code examples of how to query your database directly inside a button click.

Technically, it's a full-stack framework. But functionally, it's a frontend framework that swallowed the backend.

In the old days (2020), you had to write a separate API (pages/api/login.ts) and fetch it from your frontend.

In 2025, we use Server Actions. You can write backend logic inside your frontend components.

The "Blurry Line" in Action

Look at this code. This is a React component (Frontend), but the function inside it runs on the Server (Backend).

// This runs on the CLIENT
import { submitEmail } from "./actions";

export default function SubscribeForm() {
  return (
    <form action={submitEmail}>
      <input type="email" name="email" required />
      <button type="submit">Subscribe</button>
    </form>
  );
}

And here is the action file:

"use server"; // This directive marks it as backend code

import db from "@/lib/db";

export async function submitEmail(formData: FormData) {
  const email = formData.get("email");

  // This runs securely on your server.
  // The user NEVER sees this database logic.
  await db.user.create({ data: { email } });

  return { success: true };
}

Why This is Better

  1. No API Layer: You don't need to write REST endpoints, manage JSON serialization, or worry about HTTP verbs. It's just a function call.
  2. Type Safety: The arguments and return types are fully typed. If you change the database schema, your frontend form breaks instantly (which is good!).
  3. Security: Next.js handles the closure serialization. Secrets stays on the server.

When Do You Need a Separate Backend?

Next.js is perfect for Monoliths (which 99% of startups should be). You only need a separate backend (like Python/Go) if:

  • You are doing heavy GPU processing (training AI models).
  • You have a team of 50+ backend engineers who don't know JavaScript.

For everything else—SaaS, marketplaces, dashboards—Next.js is all you need.

VibeFast Pro leverages this pattern heavily. Our web dashboard calls database actions directly, making development feel incredibly fast.