so, caching invalidation in distributed systems, thats a tricky one. dont want stale data hanging around, right?

We're having some interesting issues with caching in our microservices setup. Basically, when one service changes data, how are other services that use that cached data supposed to know it's old news? We've tried a couple of approaches, but I'm wondering what methods folks have found work well for invalidating caches in a distributed system. What are your favorite patterns or tools for this?