Assess students' ability to apply indexing strategies and query-plan analysis to optimize SQL queries in relational databases. Expect tasks that require choosing appropriate index types (B-tree, hash, composite), interpreting EXPLAIN/EXPLAIN ANALYZE output to identify full table scans and suboptimal joins, proposing query rewrites or index changes to improve nested-loop, hash, or merge joins, and evaluating selectivity, statistics, covering/index-only scans, and read/write trade-offs including maintenance costs. Students should propose concrete changes and predict their impact on execution cost and performance.