Opensource Redis cache offers a Software as a Service which is the Redis cache. It is a secure data cache and message broker known for low latency access and higher throughput than other cache services in the market.
It can basically be used as an in-memory data store, a message broker and a nonrelational database. Azure provides you secure access to the Redis cache. It also provides you access to all the services in Microsft Azure itself.
For Azure Administrator certification, you can check this out for more insights on it.