The Stratus Redis service is accessible directly via SSH:
$redis-cli -h redis redis:6379>
From there you can run normal Redis commands, such as selecting the DB, showinfo, and so on. See https://redis.io/commands
We recommend Redis be used for all caches on Mojo Stratus (with exception to Varnish for the Magento 2 FPC) and sessions.
Via our panel, you can flush the Redis cache.