Matthew Powers gave a presentation on optimizing Delta and Parquet data lakes. He discussed the benefits of using Delta lakes such as built-in time travel, compacting, and vacuuming capabilities. Delta lakes provide these features for free on top of Parquet files and a transaction log. Powers demonstrated how to create, compact, vacuum, partition, filter, and update Delta lakes in Spark. He showed that partitioning data significantly improves query performance by enabling data skipping and filtering at the partition level.