Security and Scalability Edge Cases Questions

Understand security considerations in system design including: authentication and authorization patterns, encryption (at-rest and in-transit), preventing common vulnerabilities (SQL injection, XSS, CSRF, etc.), rate limiting and DDoS mitigation, and security in microservices. Also understand uncommon but important edge cases: how systems behave under extreme load (cascading failures, thundering herd, cache stampedes), partial failures in distributed systems, clock skew problems, Byzantine failures, and how to design systems that degrade gracefully. At Staff Level, think about security and scalability proactively when designing systems, not as an afterthought.