E.g. a single persistence.counters.proto FileDescriptor instance uses 967KB.

I'm not sure if the field documentation is useful for anything after the annotations have been parsed, but it is kept in memory, and in a hotrod-client test each DefaultCacheManager instance seem to need 3 instances of the string There is no native byte type in protobuf so it is mapped to int32. from the WrappedMessage.wrappedByte documentation.

Many lists are LinkedList instances, even though a LinkedList with 3 elements uses more memory than an ArrayList with 10 elements. Some lists are also wrapped in Collections$UnmodifiableRandomAccessList twice.

FileDescriptor HashMap fields (extendDescriptors, dependants) are never queried by key.