Caching seems to use a Dict to store the hash, which is problematic as called out in the OP: https://github.com/zgornel/Caching.jl/blob/16997d2626b42b71766cf342d9e11545243b6260/src/cache.jl#L39
And caches that support spill-to-disk can have issues with this as well.
But LRUCache.jl looks ok to me.