test-backend

BeReal technical test for backend interview

This test is based off a real feature in our backend

It should not take you more than 2 hours

Please do not fork your solution to a public repository and follow this guide to share your code, you have to do it BEFORE you code: HOW_TO_SHARE_MY_CODE.md

The discovery feature

The Discovery timeline is a crucial BeReal feature, this is where you see all the new public content of the app

The clients (mobile applications) use the GRPC service DiscoveryService.GetPosts to get the new public posts

The discovery endpoint spec

If a cursor is provided, the client wants the PAGE_SIZE posts before (older than) the cursor sorted by descending order of arrival (a scroll down in the app)

If no cursor is provided, the client wants the last PAGE_SIZE posts sorted by descending order of arrival (a pull-to-refresh in the app)

as an example:

the timeline is empty

the post 5 is posted, then the post 6 is posted, … the post 11 is posted (we add them all in the beginning for the sake of example)

PAGE_SIZE = 3

the first call with no cursor specified must yield the posts 11, 10, 9 and a cursor

using this cursor, the second call must yield the posts 8, 7, 6 and a cursor

using this cursor, the third call must yield the post 5 and a cursor

using this cursor, the fourth call must yield no posts and no cursor

Your goal

The feature is deliberately unfinished, it contains bugs and it's quite slow

Your goal is to finish the discovery.Service, as of now the GetPosts function does not handle the pagination

Challenges to keep in mind

• clients can have started scrolling from any post (they don't always ask for the last PAGE_SIZE posts)
• We don't want you to add a database engine or any go library, you can only use what Golang and this current repository provide
• keep the AddPost and GetPosts complexity low (you can reach constant complexity)
  • Over a million of posts are discoverable