Brex·Software Engineer·Technical Phone Screen·Intermediate

IntermediatePrefer not to say

Jun 2026Remote

Summary

Brex frontend coding round, one meaty React question that took up the whole session. The problem itself was well-scoped but the trade-offs discussion at the end is where things got interesting.

Questions Asked (1)

Build a React component that lets users multi-select colors from a dropdown, shows a count of selected colors, and renders a table of properties for each selected color. Also discuss trade-offs around state shape, performance with large lists, and accessibility.

System DesignTechnical Trade-offsAPI & Integrations

Author's notes

I jumped straight into useState for the selected set and felt pretty good about that.

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AI HintsAI Generated

Suggested Approach

Start by clarifying requirements and constraints, then outline a component architecture that separates state management from presentation. Implement the multi-select dropdown with a focus on accessibility and performance, and derive the selected count and table data from state. Finally, discuss trade-offs around state shape, performance optimizations for large lists, and accessibility considerations.

Pro tip: Demonstrate empathy for users with disabilities by ensuring full keyboard navigation and screen reader support, and mention how you would test these aspects. Also, show awareness of real-world constraints like API rate limits or data fetching for color properties.

1. Clarify Requirements and Constraints

Ask questions to understand the expected scale (number of colors, frequency of updates), data source for color properties, and any specific accessibility standards (e.g., WCAG). Confirm whether the component needs to be reusable or integrated with existing design system.

2. Design Component Architecture and State Shape

Decide on state shape: store selected color IDs in a Set or array, and keep color properties in a separate normalized map. Consider using useReducer for complex state logic or a state management library if the app is large. Outline component hierarchy: a container component managing state, a dropdown component, and a table component.

3. Implement Multi-Select Dropdown with Accessibility

Build a custom dropdown or use a library like Downshift or React-Select, ensuring ARIA roles (e.g., listbox, option) and keyboard interactions (arrow keys, enter, escape). Manage focus and announce changes to screen readers. For performance, virtualize the dropdown list if it contains many options.

4. Render Selected Count and Properties Table

Derive the count from the selected state and display it prominently. For the table, map over selected colors and render rows with properties. Use memoization (React.memo, useMemo) to prevent unnecessary re-renders, especially if the table is large.

5. Discuss Trade-offs and Optimizations

Compare state shape options: array vs Set for selection (Set for O(1) lookups, but serialization concerns). Discuss performance strategies: virtualization for large lists (react-window), debouncing updates, and avoiding inline functions. Address accessibility trade-offs: custom components vs native selects, and how to maintain a11y with virtualized lists.

Key Points to Mention

State shape: using a Set for selected IDs for efficient lookups, and normalizing color data to avoid duplication.
Performance: virtualizing long lists with react-window or react-virtualized, memoizing components, and using useCallback for event handlers.
Accessibility: implementing ARIA attributes (aria-multiselectable, aria-activedescendant), keyboard navigation, and focus management.
Trade-offs: controlled vs uncontrolled components, custom dropdown vs native select, and the impact on bundle size and maintainability.
Data fetching: if color properties come from an API, discuss caching, loading states, and error handling.
Testing: unit tests for state logic, integration tests for interactions, and accessibility tests with jest-axe or similar.

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