How to deploy a project written in next from json-server to vercel?

I have a project that I wrote in next js and used json-server for the fake backend. The problem is that I can't deploy the project to vercel because json-server doesn't start when building the project

I tried running multiple scripts at once using concurrently in verel, but that didn't work. Here is the command:

"scripts": {
        "build": "next build",
        "start": "next start",
        "json-server": "json-server --watch db.json --port 5000",
        "deploy": "concurrently \"npm run json-server\" \"npm run build && npm run start\"",
    },

You can create another endpoint to return fake backend because of NextJS can use as a backend service.

Your API with NextJS

// pages/api/posts.js
export default function handler(req, res) {
  const posts = [
    { id: 1, title: "Post 1", content: "This is post 1" },
    { id: 2, title: "Post 2", content: "This is post 2" },
  ];
  res.status(200).json(posts);
}

Your component:

import { useEffect, useState } from 'react';

export default function Home() {
  const [posts, setPosts] = useState([]);

  useEffect(() => {
    fetch('/api/posts')
      .then((response) => response.json())
      .then((data) => setPosts(data));
  }, []);

  return (
    <div>
      <h1>Posts</h1>
      <ul>
        {posts.map((post) => (
          <li key={post.id}>
            <h2>{post.title}</h2>
            <p>{post.content}</p>
          </li>
        ))}
      </ul>
    </div>
  );
}