Let's discuss system design questions you have encountered in interviews.
There's not a lot of questions online unlike coding questions. Let us know the questions you have come across in interviews (feel free to not reveal the company name, mostly interested in questions)
I've heard of these 2 recently:
1) Design a metrics collector and graphing system. An app uses your client api to count metrics and users can graph data over different time ranges. Asked at LinkedIn.
2) Design Twitter like system and news feed. Quite popular one.