Thank you. Could you specify what you mean by "in-memory"?
I am using
index = VectorStoreIndex.from_documents(documents)
index.storage_context.persist(persist_dir=index_path)
to save the index to file, then loading it with
index = load_index_from_storage( StorageContext.from_defaults(persist_dir="index-???"))
query_engine = index.as_query_engine()
to load it from file. Loading it also takes about 30 minutes, so if there is a way to speed that up as well that would be great. I will look into the FaissVectorStore but could you explain how an external vectorDB is different?