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Box·Machine Learning Engineer·Technical Phone Screen·Intermediate

Intermediate
May 2026

Summary

Interviewed for an MLE role at Box and the coding portion was an object-oriented design problem around file storage and lookup. Pretty straightforward as far as these things go.

Questions Asked (1)

Q1

Design a file storage and lookup system using object-oriented principles.

System DesignTechnical Trade-offs
Author's notes

Not the most grueling OOD problem I've seen.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the requirements and constraints, then design a class hierarchy that separates storage and lookup concerns. Use design patterns like Strategy and Factory to allow flexibility, and discuss trade-offs between consistency, latency, and scalability. Finally, relate the design to ML-specific needs such as feature stores or model artifact management.

Pro tip: Emphasize how your design supports ML workflows, such as versioning of models and features, and how it can integrate with existing ML pipelines. Show awareness of Box's content management focus by discussing metadata extraction and search.

1. Clarify Requirements

Ask questions to understand the scope: file types, size, access patterns, consistency needs, and ML-specific requirements like versioning or feature retrieval.

2. Define Core Abstractions

Identify key objects such as File, StorageBackend, MetadataIndex, and LookupService. Define their responsibilities and interfaces.

3. Apply Design Patterns

Use Strategy for interchangeable storage backends (e.g., local, S3, HDFS) and Factory for creating storage instances. Consider Observer for metadata updates.

4. Address Scalability and Trade-offs

Discuss partitioning, replication, caching, and consistency models. Explain trade-offs between strong vs. eventual consistency and their impact on ML use cases.

5. Integrate with ML Ecosystem

Show how the system supports ML needs: storing models, features, and experiments; enabling efficient lookups for training and inference; and ensuring reproducibility.

Key Points to Mention

  • Separation of storage and metadata indexing for efficient lookups
  • Use of design patterns like Strategy, Factory, and Observer for extensibility
  • Trade-offs between consistency, availability, and partition tolerance (CAP theorem)
  • Caching strategies to reduce latency for frequent lookups
  • Versioning and immutability for ML model and feature reproducibility
  • Integration with ML pipelines and support for metadata extraction (e.g., for search)

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