yes its needed to use a docstore
The docstore can be either SimpleDocumentStore (saved to/from disk), or a remote docstore like redis, mongodb, etc. If you use an integration, be sure to install it
pip install llama-index-storage-docstore-redis
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from llama_index.storage.docstore.redis import RedisDocumentStore
I can see them all listed in the API ref
https://docs.llamaindex.ai/en/stable/api_reference/storage/docstore/simple/