Personally I love it for cache invalidation. I used it on an older especially on project originally built without caching in mind that then added caching for immutable data without caching for mutable data in mind. It fell to me to add caching of mutable data. I found it rather convenient to put NOTIFY triggers on cached tables and have a LISTENer that will delete the corresponding rows from memcached when it gets a notification. It’s basically impossible to out-scale it in that use case because the scale is intrinsically linked to number of writes the leader in your database processes.