Frontend Developer interview. Help for interviewers (2)
July 16, 2018
If you didn’t look at Part 1 of this post please check it out.
Given a news site and its admin area. In admin area there are many users. Each user can edit a news-post.
Our goal is to make sure only one user can edit a post even if multiple users are visited the same news-post for editing. Users visited a news-post after the first user should see the “someone else is editing the post” message.
More info about the project:
- It’s not a single page application
- Backend part of the code already able to lock/unlock the post internally (we just need to call the function).
- Backend developer can implement endpoints/services a candidate ask.
Candidate usually come up with the idea to use Web Sockets. If so, you can ask candidate about how it should work.
- What message(s) should be send by web socket client to a server?
- What answer should be send by web socket server so client can know that post is blocked?
- How to make sure two users will not block the post?
- When user leaves a post who should be the next “owner” of a post if multiple other users are on a post page?
- When you have discussed all that possible implementations for web socket you can tell candidate that “unfortunately we don’t have ability to setup web socket server on our production and have to come up with something else”.
Something else is long polling technique which is basically periodic Ajax requests to a server.
- Frontend can have two Ajax requests sending by interval (one is to lock, another one is to check if locked)
- Backend should receive the “lock” and lock the post TEMPORARY.
- If no another “lock” request received by the same user we should unlock the post (temp record should be removed)
- Lock the post when there is no “lock” on the post and mark that post is locked by a user.
I hope this project and the project from Part 1 will help you to understand more about your candidate.