External Memory: Vector Stores & Databases
~15 min read
External memory persists information outside the context window — in vector stores or databases — so an agent can recall relevant facts from far earlier, or from entirely separate past sessions, without needing everything to fit in one prompt.
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Key points
- •External memory persists outside the context window — in vector stores or databases — surviving past a single session
- •Vector stores suit memory retrieved by MEANING (semantic similarity), reusing the same mechanism that powers RAG
- •Traditional databases suit memory retrieved by EXACT KEY, like structured user preferences or account details
- •Without external memory, every new session starts as a blank slate no matter how rich the in-context memory was during a prior session
- •External memory is what turns a stateless, single-session assistant into one that accumulates knowledge about a user or task over time