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Brex·Frontend Engineer·Technical Phone Screen·Senior

Senior
Jun 2026

Summary

Brex frontend round had me building a multi-select color picker UI from a mockup against a real data object. One question, but it covered a lot of ground fast.

Questions Asked (1)

Q1

Build a React UI from a provided mockup and data object: a dropdown with a checkable color list, a live-updating selection count label, and a properties table that reflects the current selection.

Technical Trade-offsSystem DesignAPI & Integrations
Author's notes

The data shape threw me a little at first.

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AI HintsAI Generated

Suggested Approach

Start by clarifying requirements and edge cases, then outline a component architecture that separates state management from presentation. Walk through the implementation step-by-step, emphasizing controlled components, derived state, and performance optimizations. Finally, discuss trade-offs and potential improvements.

Pro tip: Demonstrate awareness of accessibility and performance by mentioning keyboard navigation for the dropdown and memoization for the table rows. This shows you consider real-world usability and scalability beyond just functionality.

1. Clarify Requirements and Data Shape

Ask questions to confirm the data structure, expected interactions (e.g., multi-select, search), and any design constraints. Identify edge cases like empty selection or large datasets.

2. Design Component Hierarchy and State

Propose a component tree: a parent container holding selection state, a dropdown component, a count label, and a properties table. Decide where state lives and how it flows down via props and up via callbacks.

3. Implement Core Functionality

Describe building the dropdown with checkboxes, managing selection state (e.g., using useState or useReducer), and deriving the count and table data from that state. Emphasize controlled components and avoiding redundant state.

4. Optimize and Enhance

Discuss performance considerations like memoizing table rows or using virtualization for large lists. Mention accessibility features such as ARIA roles and keyboard support.

5. Discuss Trade-offs and Alternatives

Compare state management approaches (local state vs. context vs. external store) and component libraries vs. custom implementation. Highlight decisions based on scalability and maintainability.

Key Points to Mention

  • Controlled components and lifting state up to avoid duplication
  • Derived state for the selection count and table data to ensure consistency
  • Performance optimizations: React.memo, useMemo, and virtualization for large datasets
  • Accessibility: keyboard navigation, ARIA attributes, and focus management
  • Trade-offs between using a UI library (e.g., Material-UI) and building from scratch
  • Testing strategy: unit tests for state logic and integration tests for interactions

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