Apache Tajo is a SQL-on-Hadoop system that provides both fast interactive analysis and stable long-running extract-transform-load (ETL) jobs. It supports various data formats and storage systems. Companies like SK Telecom and Bluehole Studio use Tajo for tasks such as data warehousing, game log analysis, and music streaming data discovery. Tajo is optimized for performance and supports features like cost-based query optimization and off-heap processing. Benchmark tests show it outperforms other SQL-on-Hadoop systems like Hive and Spark SQL.