Another version of getUserByEmail as seen here: https://gajus.medium.com/how-would-you-reduce-nesting-in-this-example-http-gajus-com-blog-8-using-mysql-in-node-js-4c8c71c3a59d

getUserByEmail.js

const userQ = 'SELECT `id` FROM `user` WHERE `email` = ?'
const permissionsQ = 'SELECT `id`, `name` FROM `permission` WHERE `user_id` = ?'

const getUserbyEmail = (connection, email) => connection
  .queryAsync(userQ, [email])
  .spread(user => user === undefined
    ? [{}, {}]
    : Promise.all([user, connection.queryAsync(permissionsQ, [user.id])]))
  .then(([user, permissions]) => ({ ...user, permissions }))