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Robinhood·Frontend Engineer·Technical Phone Screen·Intermediate

IntermediatePrefer not to say
Jun 2026Remote

Summary

Robinhood frontend interview where they had me build an interactive weekly calendar UI from scratch. Pretty standard coding round but the state management requirement was where they really wanted to see your thinking.

Questions Asked (1)

Q1

Build an interactive weekly calendar UI with 7 days and hourly time slots, where clicking a cell opens a dialog to add an event, and the event then appears in that cell. State should have a single source of truth with the grid derived from it.

System DesignTechnical Trade-offsData Modeling
Author's notes

The mockup they gave made it look straightforward but the state part is where I almost tripped.

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AI HintsAI Generated

Suggested Approach

Start by clarifying requirements and constraints, then propose a normalized state model where events are stored in a flat map keyed by event ID, with a derived grid computed via selectors. Walk through the component hierarchy, data flow, and interactions, emphasizing how the single source of truth ensures consistency and simplifies updates.

Pro tip: Discuss performance optimizations like memoizing the grid derivation and using event delegation to avoid re-rendering all 168 cells on every state change. Also, mention accessibility considerations for the dialog and keyboard navigation.

1. Clarify Requirements and Constraints

Ask about expected event volume, need for persistence, time zone handling, and whether events can span multiple slots. This shows you think about real-world usage and edge cases.

2. Design the State Model

Propose a normalized state shape: an object mapping event IDs to event objects (with day, hour, title, etc.) and an array of event IDs for ordering. Explain why this avoids duplication and makes updates easy.

3. Derive the Grid from State

Describe how to compute the 7x24 grid from the event map, e.g., using a selector that groups events by day and hour. Emphasize that the grid is never stored in state, ensuring a single source of truth.

4. Define Component Architecture and Data Flow

Outline components: CalendarGrid, DayColumn, TimeSlot, EventDialog. Explain how clicking a cell sets a selected slot in state (or local UI state), opening the dialog, and how submitting dispatches an action to add an event.

5. Address Performance and Edge Cases

Discuss memoization of derived data, avoiding unnecessary re-renders, handling overlapping events, and ensuring the dialog is accessible and keyboard-friendly.

Key Points to Mention

  • Normalized state shape to avoid data duplication and inconsistencies
  • Derived grid computed via selectors or memoized functions, not stored in state
  • Unidirectional data flow: UI events dispatch actions that update state, which triggers re-render
  • Use of React context or state management library (e.g., Redux, Zustand) for global state
  • Performance optimizations: memoization, virtualization for large grids, event delegation
  • Accessibility: focus management in dialog, ARIA roles, keyboard navigation

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