app/api/create-subscription/route.js

// /api/create-subscription
import { NextResponse } from 'next/server';
import Razorpay from 'razorpay'

export async function POST(req,res){
    let instance=new Razorpay({
        key_id:process.env.RAZORPAY_KEY_ID,
        key_secret:process.env.RAZORPAY_SECRET_KEY
    })

    const result=await instance.subscriptions.create({
        plan_id:process.env.SUBSCRIPTION_PLAN_ID,
        customer_notify:1,
        quantity:1,
        total_count:1,
        addons:[],
        notes:{
            key1:'Note'
        }
    });

    return NextResponse.json(result);
}