The following system design question was asked last month in a Facebook onsite interview. I was interviewing for a mobile role.
Question
Design Instagram/Snapchat/Whatsapp stories.
Requirements
Each story is up for 24 hours max. Stories are only displayed to users once. Users can swipe to get fresh stories. The newest posted story is always displayed first.
Considerations
Users can have slow networth bandwidth. Make sure to display latest stories first. How would you prioritize stories?
My Approach
Since it was a mobile interview (Android), I mainly focused on architectural design patterns. I talked about MVC vs MVVM and mostly talked about VIPER. I didn’t have much time to discuss backend but the most I discussed was load balancing.