How would you answer an interview scenario involving GroupBy and aggregation in LINQ?

For an interview scenario involving GroupBy and aggregation, I would first clarify the business goal, scale, constraints, and the failure or quality attribute the interviewer wants to explore. GroupBy partitions elements by key and is commonly combined with Count, Sum, Average, Min, or Max. For production, keep aggregation server-side where possible and return compact summary DTOs. I would then explain the main alternatives and tradeoffs, identify likely failure modes, and describe how I would validate the solution through testing, observability, security controls, and recovery or rollback planning.