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Snap·Machine Learning Engineer·Technical Phone Screen·Senior

Senior
Jun 2026

Summary

ML engineer screen at Snap, one question deep into agent architecture. Pretty conceptual but they clearly wanted to see if you'd thought about this stuff beyond the basics.

Questions Asked (1)

Q1

How would you design or implement memory in an AI agent?

System DesignTechnical Trade-offs
Author's notes

I went straight to the short-term vs long-term split and talked about vector stores for retrieval.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the agent's requirements and constraints, then propose a layered memory architecture (short-term, long-term, episodic) with appropriate storage and retrieval mechanisms. Discuss trade-offs between different approaches (e.g., vector databases vs. relational databases, summarization vs. raw storage) and how they impact performance, cost, and scalability.

Pro tip: Emphasize the importance of memory retrieval relevance and latency, and suggest evaluating memory designs with metrics like recall@k and end-to-end task success. Show awareness of privacy and forgetting mechanisms, which are critical for production systems.

1. Clarify Requirements and Constraints

Ask about the agent's use case, expected memory size, latency requirements, and privacy considerations to tailor the design.

2. Propose a Layered Memory Architecture

Outline short-term (working memory), long-term (knowledge base), and episodic (experience) memory components, each with distinct storage and retrieval strategies.

3. Choose Storage and Retrieval Mechanisms

Select appropriate technologies (e.g., vector databases for semantic search, key-value stores for fast access) and algorithms (e.g., embedding-based retrieval, summarization) for each layer.

4. Address Trade-offs and Scalability

Discuss trade-offs between accuracy, latency, cost, and complexity; explain how the design scales with data volume and user load.

5. Define Evaluation and Maintenance

Describe metrics (e.g., retrieval precision, task success rate) and processes for updating, pruning, and forgetting memories to maintain relevance and efficiency.

Key Points to Mention

  • Different types of memory: short-term (context window), long-term (knowledge), episodic (past interactions)
  • Vector databases and embedding-based retrieval for semantic search
  • Trade-offs between summarization and raw storage (e.g., information loss vs. efficiency)
  • Latency and cost considerations in memory retrieval
  • Privacy, security, and forgetting mechanisms (e.g., GDPR compliance)
  • Evaluation metrics: recall@k, end-to-end task performance, memory footprint

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.