How to Fetch Data from an Api Handler from Another Api Handler in Nextjs?

Using Nextjs, I am struggling with fetching data from an API handler in another API handler. /api/batch.js handler retrieves some data from a MongoDB:

import middleware from '../../libs/mongodb';
import nextConnect from 'next-connect';

const handler = nextConnect();
handler.use(middleware);
handler.get(async (req, res) => {
  const {batch_uuid} = req.query
  const batch_stats = await req.db.collection('stats').find({
    'batch.uuid': uuid
  }).toArray()
  res.json(batch_stats)  
})
export default (req, res) => handler.apply(req, res)

/api/stats.js handler retrieves some data from MySQL and, based on that and on data from Mongo, it builds a payload.

A dirty fix works as below in stats.js:

const response = await fetch(')
const data = await response.json()
// use data and build another payload

However, this requires doing an http call and it does not make sense to do it for an internal endpoint. I tried calling the batch handler dirrectly, but getting undefined

const getBatch = require('./batch');
module.exports = async (req, res) => {
   const accounts = await getBatch()
   res.status(200).json({accounts})
}

What am I missing?