Caching invalidation strategies for microservices?

hey all, i've been thinking a lot about caching lately, especially how to keep data fresh across a microservices architecture. we've got services a, b, and c, where b and c depend on data from a. if a updates its data, we need to invalidate caches in b and c. we've considered event-driven invalidation via a message queue, but also looked at ttl based approaches. what are your go-to methods for this? are there specific patterns or tools you find particularly effective for keeping cached data consistent without causing too much overhead