Good points. I will try to address them. > But "knowing" this is a big part of what people mean when they say cache invalidation is hard! I can see that. Memc

Good points. I will try to address them. > But "knowing" this is a big part of what people mean when they say cache invalidation is hard! I can see that. Memcache is a look-aside cache we have at scale. There are abstractions on top to manage this complexity; and it has been fairly managable. I am sure you can come up with a complicated dependency tree that things are not obvious at all. But when you do have a very large dependency tree, any change in them can trigger cache invalidation, at which point, caching with TTL will be a better option IMO. I can see where you are coming from. > If you recognize that data can be cached in clients, and that invalidating those caches is so hard that most systems My reasoning for this being hard is different than yours I think. In my comment, it's due to indeterminism of the cluster membership. I think in that case, we are talking about different problems.