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Snap·Machine Learning Engineer·Technical Phone Screen·Senior

Senior
May 2026

Summary

Snap ML engineer interview, got a system design style question about handling long inputs in generative models. Pretty technical, felt like they wanted to see if you'd actually thought about this in practice rather than just reciting textbook answers.

Questions Asked (1)

Q1

Your generative model needs to handle inputs that are longer than what the context window supports. How do you deal with that?

System DesignTechnical Trade-offsAdaptability & Ambiguity
Author's notes

I went straight to chunking and retrieval augmentation, which felt safe but maybe too surface level.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the constraints: model type, context window size, latency and cost requirements, and whether the task needs full-document understanding or just relevant snippets. Then propose a layered solution that combines input reduction (chunking, retrieval, summarization) with architectural adaptations (sliding window, sparse attention, memory mechanisms), and discuss trade-offs for each approach.

Pro tip: Emphasize that the best solution depends on the task: for QA, retrieval-augmented generation (RAG) often suffices; for summarization, hierarchical chunking works well; for long-form generation, memory mechanisms or recurrence may be needed. Show you can adapt to constraints rather than defaulting to one method.

1. Clarify requirements and constraints

Ask about the model architecture, context window size, input length distribution, latency and cost budgets, and the specific task (e.g., QA, summarization, generation). This ensures your solution is tailored.

2. Consider input reduction techniques

Discuss methods like chunking with overlap, retrieval-based selection of relevant passages, or summarization of chunks before feeding to the model. These reduce input length while preserving key information.

3. Explore architectural adaptations

Mention approaches like sliding window attention, sparse attention (e.g., Longformer, BigBird), recurrence, or memory mechanisms (e.g., Transformer-XL, compressive memory) that extend effective context without retraining from scratch.

4. Evaluate trade-offs and choose a hybrid approach

Compare methods on accuracy, latency, cost, and implementation complexity. Often a hybrid (e.g., RAG + chunking) works best. Justify your choice based on the clarified requirements.

5. Plan for evaluation and iteration

Propose metrics (e.g., task-specific accuracy, latency, cost) and a strategy to test different approaches, such as A/B testing or offline evaluation, to ensure the solution meets production needs.

Key Points to Mention

  • Chunking strategies (fixed-size, semantic, recursive) and handling inter-chunk dependencies
  • Retrieval-augmented generation (RAG) for selecting relevant context
  • Summarization or compression of long inputs before feeding to the model
  • Architectural solutions: sliding window, sparse attention, memory mechanisms
  • Trade-offs: accuracy vs. latency vs. cost vs. implementation complexity
  • Evaluation metrics and iterative testing to validate the approach

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