Why I moved from REST to Server Actions in Next.js 15

For years, the standard way to build a React application with a backend was to build a REST API. You create an endpoint like /api/users, write a fetch call on the frontend, handle loading states, handle error states, and manually invalidate caches.

It's tedious. With Next.js 15, I finally took the plunge and migrated my entire architecture to Server Actions. I deleted my /api folder entirely.

What is a Server Action?

A Server Action is essentially an RPC (Remote Procedure Call). It allows you to define an asynchronous function on the server and call it directly from a client component, as if it were a normal JavaScript function.

typescript
// actions.ts
'use server'

import { getDb } from '@/lib/mongodb'

export async function likePost(blogId: string) {
  const db = await getDb()
  await db.collection('blogs').updateOne(
    { _id: new ObjectId(blogId) },
    { $inc: { likes: 1 } }
  )
  return { success: true }
}

Then, on the client:

tsx
// LikeButton.tsx
'use client'
import { likePost } from './actions'

export default function LikeButton({ id }) {
  return <button onClick={() => likePost(id)}>Like</button>
}

The Benefits

The transition requires a shift in mental models—you have to think about security at the function level rather than the endpoint level—but the increase in developer velocity is undeniable.