so, when should we think about using a distributed cache instead of just a local one? like, what's the tipping point

Hey everyone, I've been thinking about caching strategies lately. For some smaller services, a local in-memory cache, maybe Guava Cache or just a simple map, seems fine. But as things scale up, or when multiple instances need to share cache state, a distributed cache like Redis or Memcached becomes the way to go. What are your general rules for deciding when to switch from local to distributed caching? Are there specific performance levels, data consistency needs, or how services talk to each other that tell you it's time for the move?