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