Design a user activity query system

## Problem Design a query system that allows internal consumers (e.g., customer support, risk/fraud, data analysts) to retrieve a given user's **search** activity and **order** activity. The query must support filtering by: - **Time**: a time range (start/end) - **Geography**: a location constraint (e.g., bounding box or radius around a point) ## Data to Query Assume two event types: 1. **Search events**: (user_id, timestamp, query_text, location_lat/lng, device/session metadata) 2. **Order events**: (user_id, order_id, timestamp, items/amount, shipping/delivery location, payment metadata) ## Required Capabilities - Given `(user_id, time_range, geo_filter)`, return matching search events and order events. - Sort results by timestamp, and paginate. - Support querying either event type separately or both together. ## Non-Functional Requirements (state assumptions) - Low latency interactive queries (e.g., p95 < 1–2s for typical ranges like last 7–30 days). - Handle large volume of events (search events are high-cardinality and high-write; orders are lower volume but strongly consistent in the source of truth). - Data is privacy-sensitive; enforce access controls and auditing. ## Deliverables Describe: - APIs (request/response) - Data model and indexing strategy for time + geo queries - Storage choices and overall architecture (ingestion, serving, retention) - Scalability, consistency, and operational considerations - Key trade-offs and edge cases