function doLotsOfStuff() {
  // Call two asynchronous functions which return promises.
  return Promise.join(
    readFromDB(),
    requestFromService()
  )
  .spread((dbResponse, serviceResponse) => {
    // Do something with both the dbResponse and the serverResponse.
    // Return only dbResponse as example.
    return dbResponse;
  })
  .catch(err => {
    // Handle errors.
   });
}

doLotsOfStuff()
.then((dbResponse) => doSomethingElse(dbResponse))
.then((somethingElseResponse) => anythingElse());