Design a fitness activity tracking app where followers can see current trails, users can query top activities by time range, and leaderboards are supported. <details> <summary>Hint 1</summary> Start by stating assumptions, then work from requirements to trade-offs and validation. </details> <details> <summary>Hint 2</summary> Use concrete examples from the prompt and make edge cases explicit. </details> ### Constraints & Assumptions - Preserve the source scope; do not assume extra company-specific systems. - Focus on interview reasoning, correctness, and operational trade-offs. - Explain how you would validate the answer with examples, metrics, or tests. ### Clarifying Questions to Ask - What exact user, system, or business goal should this solve? - What scale, latency, reliability, or privacy constraint matters most? - What existing infrastructure or code must the solution integrate with? - What output or behavior will the interviewer use to judge success? ### What a Strong Answer Covers ```premium-lock What a Strong Answer Covers ``` ### Follow-up Questions - How would your answer change at 10x scale? - What would you monitor in production? - What edge case is easiest to miss? - What would you simplify if this were a 60-minute implementation round?