If your service is hosted on a single machine, chances are that in-memory caching will have a better performance and will be easier to implement.
On the other hand, there are two situations where local caching is not enough:
- As soon as your service starts to be hosted on multiple servers, which is the case for most services hosted in production, you may need to implement either distributed or centralized caching in order for your services to share the same cache.
In this case, if your language/framework/infrastructure doesn't already have the feature (such as AppFabric in Microsoft community), Redis appears an excellent alternative.
- Redis has much more features than ordinary cache systems. Have you seen the list of Redis commands? Instead, most caching systems are limited to three actions: add, get, remove.
If you need those additional features, Redis is obviously a solution to your needs.