Sigmacomputing·Frontend Engineer·Technical Phone Screen·Senior

Senior

Jun 2026

Summary

Sigma Computing frontend interview that went way deeper into CS fundamentals than I expected. The whole session was basically one big design problem around spreadsheet internals, which felt pretty on-brand for a company that builds spreadsheet software.

Questions Asked (1)

Design and implement a Spreadsheet class with a finite ordered set of columns, sparse storage for non-zero cells, and an API supporting get, set, and printFirstNLines operations. The set method should accept either integer values or formula strings referencing other cells.

System DesignAlgorithms & Data StructuresTechnical Trade-offs

Author's notes

This was the whole interview.

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AI HintsAI Generated

Suggested Approach

Start by clarifying requirements and constraints, then outline a high-level design using a sparse map for storage and a dependency graph for formulas. Implement the core API with lazy evaluation and cycle detection, and discuss trade-offs like eager vs lazy evaluation and error handling.

Pro tip: Demonstrate awareness of frontend performance by mentioning how sparse storage and lazy evaluation reduce memory and computation, and how you'd handle UI updates efficiently with change detection.

1. Clarify Requirements

Ask about column ordering, formula syntax, error handling, and expected operations. Confirm whether formulas can reference other formulas and if circular references should be prevented.

2. Design Data Structures

Use a Map of Maps (row -> column -> value) for sparse storage, and a separate Map for formulas. Consider a dependency graph to track cell relationships for evaluation.

3. Implement Core API

Implement get, set, and printFirstNLines. For set, parse formulas, update dependencies, and mark affected cells dirty. For get, evaluate lazily if needed, with cycle detection.

4. Handle Formulas and Evaluation

Parse formula strings to extract cell references, build a dependency graph, and use topological sorting or recursive evaluation with memoization. Detect cycles and throw errors.

5. Discuss Trade-offs and Optimizations

Compare eager vs lazy evaluation, memory vs speed, and error handling strategies. Mention how this design supports frontend needs like efficient rendering and updates.

Key Points to Mention

Sparse storage using Map of Maps to save memory for non-zero cells
Formula parsing and dependency graph for evaluation order
Cycle detection to prevent infinite loops
Lazy evaluation to defer computation until needed
Error handling for invalid formulas or circular references
Performance considerations for frontend rendering and updates

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