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HarveyAI·Machine Learning Engineer·Technical Phone Screen·Intermediate

Intermediate
Jun 2026

Summary

Interviewed for an MLE role at HarveyAI and got a spreadsheet design problem that apparently circulates on 1point3acres. Part one was pretty approachable, just HashMap-based get and set cell operations.

Questions Asked (1)

Q1

Design a spreadsheet system with get_cell and set_cell operations.

System DesignAlgorithms & Data StructuresData Modeling
Author's notes

Part one wasn't bad.

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AI HintsAI Generated

Suggested Approach

Start by clarifying requirements: what operations are needed (get/set), data types, concurrency, persistence, and scale. Then propose a data model (e.g., sparse matrix or dictionary of cells) and discuss trade-offs for different access patterns. Finally, outline the API design, error handling, and potential optimizations like caching or indexing.

Pro tip: Demonstrate awareness of real-world spreadsheet challenges like formula dependencies, circular references, and concurrent edits, and suggest how to handle them (e.g., topological sort for recalculation, versioning for concurrency).

1. Clarify Requirements

Ask about expected scale (number of cells, users), data types (numbers, strings, formulas), operations (get, set, delete, range queries), and non-functional requirements (latency, consistency, persistence).

2. Design Data Model

Propose a storage structure: a 2D array for dense sheets or a hash map (dictionary) keyed by cell coordinates for sparse sheets. Discuss memory and access time trade-offs.

3. Define API and Operations

Specify the interface for get_cell(row, col) and set_cell(row, col, value), including error handling for invalid coordinates or types. Consider batch operations and range queries.

4. Address Advanced Features

Discuss formula evaluation, dependency tracking, and recalculation strategies. Mention concurrency control (e.g., locking, optimistic concurrency) and persistence options.

5. Optimize and Scale

Suggest optimizations like caching frequently accessed cells, indexing for range queries, and sharding for large sheets. Consider trade-offs between consistency and availability.

Key Points to Mention

  • Sparse vs dense representation and memory efficiency
  • Time complexity of get and set operations (O(1) for hash map, O(1) for array with known dimensions)
  • Handling formulas and dependency graphs (e.g., directed acyclic graph, topological sort)
  • Concurrency control mechanisms (locking, MVCC) for multi-user editing
  • Persistence and durability (write-ahead log, snapshots)
  • API design principles: idempotency, error codes, and validation

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