"Design a data platform for e-commerce."
Cover: ingestion (orders, products, users), storage (lakehouse/warehouse), transformation (medallion layers), serving (BI, ML), quality/observability.
"Design real-time analytics for a mobile app."
Cover: event ingestion (Kafka), stream processing, OLAP store (Druid/ClickHouse), dashboard layer.
"Design a feature store for ML."
Cover: offline features (batch), online features (low-latency), consistency between them, versioning.
Always discuss: scale requirements, latency needs, cost constraints, team size. Ask clarifying questions first.