Amazon·Software Engineer·Onsite - System Design / Architecture·Senior

SeniorPrefer not to say

Apr 2026

Summary

Amazon system design interview for a software engineering role, focused entirely on UI component architecture. One question, but it went deep fast and I wasn't fully prepared for how much they cared about accessibility and API design.

Questions Asked (1)

Design and implement a reusable dialog (modal) component for a UI component library. Walk through the public API, internal state management, DOM structure, keyboard interaction, accessibility, and how you'd support theming.

System DesignTechnical Trade-offsAPI & Integrations

Author's notes

This felt like a frontend system design question disguised as a coding question and I kept trying to write code when they really wanted me to think out loud about the API surface first.

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AI HintsAI Generated

Suggested Approach

Start by clarifying requirements and constraints (e.g., framework, accessibility level, theming needs), then walk through the component's public API and internal state management, followed by DOM structure, keyboard interactions, accessibility, and theming. Emphasize trade-offs and justify decisions based on Amazon's scale and customer obsession.

Pro tip: Demonstrate deep accessibility knowledge by mentioning focus trapping, ARIA roles, and screen reader considerations, and discuss how you'd test these aspects. Also, highlight how your design supports Amazon's diverse customer base and internationalization needs.

1. Clarify Requirements and Constraints

Ask questions to understand the expected usage, framework (e.g., React, Vue), accessibility standards (WCAG), theming requirements, and performance considerations. This shows you think before coding.

2. Define Public API and State Management

Outline the component's props (e.g., isOpen, onClose, title, children) and internal state (e.g., focus management, animation states). Discuss controlled vs uncontrolled patterns and how to handle edge cases.

3. Design DOM Structure and Keyboard Interactions

Describe the HTML structure (e.g., overlay, dialog container, close button) and keyboard support (e.g., Escape to close, Tab trapping, Enter/Space activation). Mention focus restoration on close.

4. Ensure Accessibility and Theming

Explain ARIA attributes (role='dialog', aria-modal, aria-labelledby), screen reader announcements, and theming via CSS variables or design tokens. Discuss how to support dark mode and custom themes.

5. Discuss Testing and Trade-offs

Mention unit, integration, and accessibility tests (e.g., using jest-axe). Highlight trade-offs like performance vs. flexibility, and how you'd document and version the component for reuse.

Key Points to Mention

Focus management: trapping focus within the modal and restoring focus to the trigger element on close.
ARIA attributes: role='dialog', aria-modal='true', aria-labelledby and aria-describedby for labeling.
Keyboard interactions: Escape key to close, Tab/Shift+Tab to cycle focus, Enter/Space to activate buttons.
Theming: use CSS custom properties (variables) or a theme provider to allow customization without breaking encapsulation.
Controlled vs uncontrolled component patterns: supporting both for flexibility.
Performance considerations: lazy rendering, avoiding unnecessary re-renders, and using portals to avoid stacking context issues.

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