High-Level Design (system design) rounds at Google show up mainly from SDE-2/L4 upward, and lean toward familiar, well-scoped services rather than open-ended prompts. Interviewers reward a structured approach: requirements first, then API design, data model, and scaling/caching, in that order.
Problem 1Design a URL-Shortening Service
Design a service that takes a long URL and returns a short, unique alias for it, and redirects visitors from the short alias back to the original URL — built to handle high-throughput reads and writes.
Requirements to clarify first
- Do short codes need to be unpredictable (hard to guess/enumerate), or is a simple counter-based code acceptable?
- Should the same long URL always map to the same short code, or can two requests for the same URL get two different codes?
- What's the expected read:write ratio? (Real traffic on a shortener is almost always read-heavy — redirects vastly outnumber new links created.)
Only one verified, fully-detailed system-design prompt has been reviewed for Google so far — more will be added as additional candidate reports are verified.