SoFi·Frontend Engineer·Technical Phone Screen·Intermediate

Intermediate

Jul 2026

Summary

Frontend coding round at SoFi where the whole thing was building a typeahead/autocomplete component using just HTML and CSS, no JS frameworks, no libraries. Pixel-matching a design spec under interview pressure is a different kind of stress than algorithm questions.

Questions Asked (1)

Build a typeahead autocomplete input component using only HTML and CSS to match a given design mockup, including input styling, placeholder behavior, dropdown panel layout, and hover/focus states.

Technical Trade-offsSystem Design

Author's notes

The CSS-only constraint sounds manageable until you're staring at a dropdown that needs to appear on focus with no JavaScript.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the constraints and design mockup details, then walk through a pure HTML/CSS implementation using semantic markup and CSS pseudo-classes for interactivity. Explicitly address the trade-offs of a CSS-only approach, such as limited dynamic filtering and accessibility gaps, and propose how you would enhance it with JavaScript while keeping the CSS foundation.

Pro tip: Demonstrate awareness that a production typeahead at a fintech like SoFi must handle accessibility (ARIA combobox pattern) and performance (debouncing, virtualized lists), and mention that CSS-only solutions are great for prototypes but need JS for real-time data and keyboard navigation.

1. Clarify requirements and constraints

Ask about the design mockup specifics (input size, dropdown styling, hover/focus colors) and whether JavaScript is allowed. Confirm the expected behavior for placeholder, focus, and hover states.

2. Outline HTML structure

Propose a semantic structure: a container with an input and a list of suggestions, using appropriate roles (e.g., role='combobox', 'listbox', 'option') for accessibility. Explain how to use labels and placeholder attributes.

3. Implement CSS styling and states

Describe styling the input (padding, border, focus ring), placeholder (::placeholder), dropdown panel (absolute positioning, box-shadow, border-radius), and hover/focus states using :hover, :focus, and :focus-within. Use CSS to show/hide the dropdown based on input focus or a checkbox hack.

4. Address interactivity limitations and trade-offs

Explain that pure CSS cannot filter suggestions based on input value or handle keyboard navigation. Discuss using JavaScript for dynamic filtering, debouncing, and ARIA live regions, while keeping CSS for visual states.

5. Discuss scalability and production readiness

Mention performance considerations like virtual scrolling for large datasets, caching, and server-side search. Highlight the importance of accessibility testing and cross-browser compatibility.

Key Points to Mention

Semantic HTML and ARIA roles for accessibility (combobox, listbox, option, aria-expanded, aria-activedescendant)
CSS pseudo-classes for states: :focus, :hover, :focus-within, ::placeholder, and using :checked for toggling dropdown visibility
Trade-offs of CSS-only: no dynamic filtering, no keyboard navigation, limited screen reader support
JavaScript enhancements: debouncing input, fetching suggestions, keyboard navigation (arrow keys, enter, escape), and managing focus
Performance optimizations: virtualized lists, caching, and minimizing DOM updates
Design fidelity: matching mockup spacing, colors, typography, and transitions for hover/focus

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