account/src/middleware/ratelimit.js

const crypto = require('crypto');
const ratelimit = require('express-rate-limit');

module.exports = ratelimit({
	windowMs: 60 * 1000,
	max: 1,
	keyGenerator: request => {
		const data = request.headers['x-nintendo-device-cert'];
		return crypto.createHash('md5').update(data).digest('hex');
	}
});