Presto is an open source distributed SQL query engine for running interactive analytic queries against various data sources. Redis is an open-source in-memory key-value data server.
The Redis connector allows querying of live data stored in Redis via SQL queries. This can be used to join data between different systems like Redis and Hive in a single SQL statement.
The Redis/Presto capability allows Groupon to provide value for both consumers and merchants by providing real-time insights via matching real-time customer data such as store foot traffic against historical data stored in Apache Hadoop.
Last year Groupon also added Kafka support to Presto.