Phase 7: Agent Memory Systems · 50 min · Python · Anthropic SDK · chromadb
Memory Architecture Taxonomy
The right memory type for the right information is the difference between a chatbot and an assistant.
Hiring signal: Memory architecture is what makes agents feel like real assistants rather than stateless chatbots. Any AI product that involves ongoing user relationships — personal assistants, learning tools, project collaborators — needs engineers who can design a memory system. This is a system design question that appears in senior AI engineer interviews.
What you will learn
- Map the four memory types to their implementation: in-context, episodic, semantic, procedural
- Identify which memory type fits each use case
- Explain the tradeoffs of each memory type: cost, retrieval speed, staleness risk
The Problem
You use the same AI assistant every day for 6 months. It still asks for your name. It still recommends the same things you told it you don't like. It has no memory.
Meanwhile, your best human collaborator remembers your preferences, your past decisions, and the context of ongoing projects — without you re-explaining. This lesson is the architecture that makes AI remember like a person.
The insight: human memory is not one system. It's four. Each handles a different kind of information with different retrieval characteristics. Agent memory works the same way.
Four Memory Types
In-context memory (working memory): Everything in the current context window. Fast (zero latency), but lost at session end. Capacity: 100k–200k tokens for modern models. Use for: the current conversation, retrieved documents, temporary computation results.
Episodic memory: Records of specific past events. "On 2025-11-14, user asked about deployment options and we decided on Vercel." Stored in a vector DB or key-value store. Retrieval: semantic search over past episodes. Permanent until explicitly deleted.
Semantic memory: General knowledge, facts, user preferences. "User prefers Python over JavaScript. User works in the healthcare domain. User dislikes verbose explanations." Stored as structured facts. Retrieval: direct lookup or similarity search.
Procedural memory: How to do things. Stored as tool definitions, system prompt rules, or fine-tuned model weights. Slowest to update — requires redeployment or retraining. Most durable — doesn't fade or get stale the way episodic memories do.
Unlock the full lesson
You've read the first 2 sections. The rest of this lesson covers Memory Type Selection Guide, Tradeoffs, Build It, What to Practice — plus a hands-on lab, quiz, and project artifact.
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