Google System Design interview questions target your ability to design large, reliable, and maintainable systems rather than to memorize specific product internals. Interviewers look for structured thinking about requirements, clear APIs and data models, capacity and latency estimates, scaling strategies, failure modes, and observability. Expect a 45–60 minute, open‑ended conversation where you start with clarifying questions, sketch a high‑level architecture, then iteratively drill into hotspots (datastore choices, sharding, caching, consistency, load balancing, and recovery) while defending trade‑offs under follow‑up challenges. Effective interview preparation balances breadth and depth: practice a handful of canonical systems (URL shortener, chat service, streaming, search, document collaboration) and rehearse quantifying traffic and storage, estimating RPS and capacity, and naming concrete failure scenarios. Use timed sketching on a whiteboard or shared doc, run mock interviews that force you to explain trade‑offs, and incorporate observability, SLIs/SLOs, and deployment considerations into every design. Aim to make assumptions explicit, iterate when challenged, and show pragmatic engineering judgment.