AWS Certified Data Engineer Associate DEA-C01 Practice Question

Defining session_id as the DISTKEY places rows that share the same session identifier on the same node, so joins to the sessions dimension on that column are mostly local and avoid the network. A COMPOUND SORTKEY on event_time keeps rows for the same time range physically adjacent, allowing Redshift to skip blocks when queries restrict on recent days. The combination directly addresses the two dominant access patterns (join on session_id, range filter on event_time) while keeping distribution overhead low. Using event_time as the DISTKEY would not help the join, EVEN distribution would still require network shuffling, and DISTSTYLE ALL would replicate billions of rows and greatly increase storage and load times. Interleaved sort keys add overhead and offer no advantage when the primary filter is on a single column.