Learn how to solve the distributed cache invalidation problem in .NET 9 by implementing a Redis Pub/Sub backplane to synchronize HybridCache instances across multiple nodes.

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Milan Jovanović

Distributed cache invalidation is a critical challenge when running multiple application instances with HybridCache in .NET 9. While HybridCache combines fast in-memory (L1) and distributed (L2) caching, it doesn't automatically synchronize local caches across nodes, leading to stale data. The solution involves implementing a Redis Pub/Sub backplane that broadcasts invalidation messages to all nodes. When data changes on one node, it publishes a message containing the cache key; all other nodes subscribe to this channel and remove the key from their local cache. The implementation requires a publisher service (RedisCacheInvalidator) and a background subscriber service (CacheInvalidationService) that listens for invalidation messages. Alternatively, FusionCache provides a mature, built-in backplane solution with HybridCache compatibility.

Solving the Distributed Cache Invalidation Problem with Redis and HybridCache