Resque is a Redis-backed Ruby library that allows placing background jobs in queues to be processed later. It uses workers that poll Redis for new jobs and execute retrieved jobs. Worker pooling allows executing jobs concurrently using multiple workers. Jesque is a Java port of Resque that also uses worker pooling but is not robust, as workers can die permanently. RobustWorkerPool is a library for Jesque that monitors worker status and replaces any died workers, making the pooling more robust.