Google System Architect Mock Interview

Tell us about a time you had to design or evolve a large-scale distributed system under strict reliability and latency requirements—what tradeoffs did you make, how did you measure success, and what would you do differently today?

Google runs at massive scale; describe how you would architect a globally distributed service (e.g., search, ads, or Maps) that must handle sudden traffic spikes while maintaining SLOs—what components would you include (routing, caching, data consistency, backpressure), and how would you validate the design?

Suppose you inherit an existing system with high operational burden (frequent incidents, slow rollouts, unclear ownership). Walk us through your approach to diagnosing root causes and improving the architecture—how would you balance quick wins with longer-term refactors?

A product team wants to add a feature that requires joining data across multiple services, but the current architecture is optimized to avoid cross-service coupling. How would you decide between options like denormalization, event-driven replication, or runtime joins, and what data consistency strategy would you choose?

Imagine a scenario where a critical dependency (e.g., a shared datastore or internal RPC) starts returning degraded results due to a partial outage. What would your system architecture and incident playbook do to preserve user experience, contain blast radius, and support safe rollback?