Azure Redis Cache in 2 minutes
This is very quick summary why cache and what it brings. what value any cache would add to application and obvious answer is it improves application performance and some extend improves availability of your application. incase your backup db is not available cache would serve request based on what data it has.
What type of data would should cache? all what we have in DB? not for sure. the data that do not change frequently and not something like stock market related.
How do we invalidate date? as most of the data would change and that needs to be updated in cache too. we can leverage application config and cache config to implement invalidation policy so based on requirement it will fetch fresh data from DB.
Azure Redis cache is cloud version which is PaaS offering where it is fully managed by Azure. it is based on open-source redis cache which has large community support. it also support many data type that includes Strings, Hashes, Lists, Sets and more...
Azure Redis is highly available offering which has capability to create Geo-replication for high availability, Cluster to handle load and Data Persistence for Backup purpose. we can also configure session state in cache to improve performance.
That's all quick summary...what else update in comment below.