holochain_wasmer has three caches:

• a file system cache where serialized modules are stored
• an in-memory cache where serialized modules are stored
• an in-memory cache where deserialized modules are stored

The in-memory cache of serialized modules is redundant. If the module is not in the deserialized cache, which is the fastest way to obtain an executable module, it can either be found on the file system or needs to be compiled from wasm. There's no need to store it in serialized form in-memory.