Start by clarifying requirements and constraints, then outline a high-level design covering load balancing algorithms, health checks, and scalability. Dive into trade-offs for key components like layer 4 vs layer 7, and discuss how to handle failures and dynamic scaling.
Pro tip: Emphasize that a load balancer is a distributed system itself, so you must consider its own high availability and failure modes. Mention that Google's Maglev is a real-world example of a scalable load balancer.
Ask about expected traffic volume, latency requirements, protocol (TCP/UDP/HTTP), and whether it's for internal or external use. This shapes the design.
Sketch the architecture: clients, load balancer, backend servers. Decide on layer 4 vs layer 7, and whether to use a centralized or distributed approach.
Discuss algorithms like round robin, least connections, consistent hashing, and their trade-offs. Explain how to handle session persistence if needed.
Describe how to detect unhealthy backends (active/passive checks) and remove them from rotation. Discuss how the load balancer itself achieves high availability.
Address how to scale the load balancer (horizontal scaling, anycast, DSR) and optimize performance (connection pooling, caching, hardware acceleration).
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.