Focus areas: Distributed systems, data processing, search infrastructure, ML pipelines.
What they value: Scale thinking (billions of users), algorithmic efficiency, handling edge cases, infrastructure awareness.
Common topics: Design a search system, design a distributed cache, design a data pipeline, design YouTube's recommendation system.
Tips: Show math. Estimate QPS, storage, network bandwidth. Discuss trade-offs explicitly. Mention consistency models. Google wants to see you think at their scale.