In Delta Lake, what does the OPTIMIZE command do?

• A. It compacts small files into larger files to improve read performance
• B. It creates new partitions
• C. It rewrites the table schema
• D. It deletes data

Answer: (A)

Delta Lake stores data as many Parquet files, and having a lot of tiny files adds metadata overhead and slows reads. The OPTIMIZE command consolidates those small files into fewer, larger Parquet files, which reduces IO overhead and improves read performance. You can also pair it with ZORDER BY to physically organize data by specific columns for faster range and filter queries. It doesn’t create new partitions, rewrite the table schema, or delete data—those tasks are handled by other commands. So the main effect is compacting small files into larger ones to boost query efficiency.