I am trying to implement user registration and am wondering if I did this correctly and if I am doing the mongodb connection correctly since Ive heard something about keeping the connection open but not really sure what that means yet. If anyone can take a look and lmk I would appreciate it.

src > app > api > registerUser > route.ts

import { connectToMongoDB } from "@/lib/mongodb";
import { NextResponse } from "next/server";

import User from "@/models/User";

export const POST = async (request: Request) => {
   try {
      const { name, email, password } = await request.json();

      // Check if all fields are filled
      if (!name || !email || !password) return NextResponse.json({ message: "Please fill in all fields." }, { status: 400 });

      await connectToMongoDB();

      // Check if user already exists
      const userAlreadyExists = await User.findOne({ email });
      if (userAlreadyExists) return NextResponse.json({ message: "User already exists." }, { status: 409 });

      // Create new user
      const newUser = new User({ name, email, password });
      await newUser.save();

      return NextResponse.json({ message: "User registered." }, { status: 201 });
   }
   catch (error) {
      return NextResponse.json(
         { message: "Server error." },
         { status: 500 }
      );
   }
}

src > lib > mongodb.ts

import mongoose from 'mongoose';

// MongoDB connection
export async function connectToMongoDB() {
   try {
      const mongoDBConnection = await mongoose.connect(String(process.env.MONGODB_URI))
      console.log('MongoDB connected');
      return mongoDBConnection;
   }
   catch (error) {
      throw new Error('Error connecting to MongoDB: ' + error);
   }
}