From the interviewers point-of-view, the goal is to assess a person's:

1. technical design skills
2. ability to collaborate
3. work under pressure
4. resolve ambiguity

Red flags in interview:

• over-engineering: delight in design purity, ignore trade-off
• narow mindedness, stubbornness
• giving out answer without thinking & talking through the problem

Ask the right questions:

• what specific features
• how many users, traffic
• scaling plan
• tech stack (mobile/web): language, cache service

Make a initial design and ask for feedback

• draw box diagrams
• back-of-the-envelope estimation on storage
• look for edge cases

Depending on job level, the interview may focus on high-level design, or performance characteristics (bottleneck)

• do not try to explain technical details (e.g. how an algorithm works)
• careful with time management. Don't get carried away by trivia

Answer follow-up questions, including:

• identify system bottleneck and potential improvement
• recap of design (especially if more than one solutions are suggested)
• failure cases
• operation and monitoring (metrics, error logs)
• scale to next level

• Design Rate Limiter
• Design Consistent Hashing
• Design Key-Value Store
• Design Unique ID Generator
• Design URL Shortener
• Design Web Crawler
• Design Notification System
• Design News Feed
• Design Chat Systen
• Design Auto-complete
• Design YouTube
• Design Google Drive

• hbase intro
• mongodb intro

• Server Sent Events