Azure Cache for Redis provides an in-memory data store based on the popular open-source software Redis.
- **Session Store:** Keep user session data out of your app server's RAM so you can scale horizontally.
- **Database Caching:** Store the results of heavy SQL queries to reduce DB load.
- **Pub/Sub:** Real-time messaging between your microservices.
Use the **StackExchange.Redis** NuGet package. In modern ASP.NET Core, it's best practice to use the IDistributedCache interface. This allows you to swap between a local memory cache and Azure Redis with a single configuration change, making your code highly portable.
Q: "Should I use the Premium tier?"
Architect Answer: "Only if you need **Data Persistence** (saving the cache to disk) or **Clustering** (splitting data across multiple nodes for terabyte-scale). For most standard .NET APIs, the **Standard Tier** with its built-in replication (Master/Slave) provides the 99.9% availability you need for a fraction of the cost."