Popular System Design Problems to solve

1: Design an elevator system 
2: Design a rate limiting system 
3: Design a photo hosting system / Instagram.
4: Design a distributed cache 
5: Design a Tiny URL 
6: Design a Web search engine 
7: Design Youtube/Netfilx video hosting
8: Design a Facebook style news feed 
9: Design a Twitter style news feed 
10: Design a WhatsApp Messaging Service
11: Design Auto-complete system
12: Design SplitWise
13: Design Uber or Food Delivery system.
14: Design a Recommendation System.
15: Design an e-commerce System.

Aim : 10K or 100K request per second.