TOPIC

Frontend

These are the same questions found in the library, grouped here by the capability each one mainly examines.

47 questions

A · Professional problem solving and implementation46

A sign-up form ends up in inconsistent states because of duplicate submissions and weak-network retries. How would you map its states and transitions, and decide which logic to extract into its own unit?Coding and abstraction
Implement a retry wrapper that retries by error type, supports a maximum attempt count, backoff, and cancellation, and does not overwhelm the dependency. Define the interface before coding, then explain how to make clocks, waits, and tests deterministic.Coding and abstraction
After a page sits idle, the first request is much slower than later ones. What network-level causes could explain it, and how would you tell them apart?Computer-science foundations
The first screen of an image-heavy page opens slowly. How would you work backwards from the symptom to the cause, and what would each improvement cost?Computer-science foundations
Your endpoint works in local tests, but during integration a frontend colleague insists it errors or returns nothing. What means do you use to locate the problem, and how do you produce evidence the other person will accept?Debugging
After splitting a large frontend bundle into several smaller ones, the first screen got slower. What causes would you suspect, and how would you verify them?Debugging
A company’s frontend projects live in separate repositories, and someone proposes merging them into a monorepo. How would you decide whether to do it, and how would you validate it in steps?Engineering systems
The framework allows concurrent background UI updates, but a slow response occasionally overwrites a newer selection. How would you design concurrent state updates?Coding and abstraction
A complex form has field validation, cross-field rules, and server errors that overwrite one another during edits. How would you divide framework state from business state?Coding and abstraction
Several pages share server data and framework caching reduces requests, but stale results appear after users switch accounts. How would you design cache keys and invalidation boundaries?Coding and abstraction
After a frontend framework upgrade, compilation succeeds, but render timing, default caching, or side-effect order changes. How would you verify product behavior remains correct?Engineering systems
A user signs in within one child app but loses permissions or session state when switching to another. How would you design the boundary for shared auth context?Engineering systems
One app emits an “order completed” event, but other modules interpret it differently, causing duplicate requests and divergent page state. How would you define a cross-app event contract?Engineering systems
Users report a blank page after navigating across apps, while each team’s monitoring appears healthy. How would you establish end-to-end observability?Engineering systems
After independently developed apps are integrated, styles collide, themes differ, and overlays are clipped. How would you choose a style-isolation strategy?Engineering systems
Several frontend modules build independently, but releases still require coordination. What evidence would show they have a real independent delivery boundary?Engineering systems
A large frontend makes parallel delivery difficult, but splitting it into several apps at once is risky. How would you plan an incremental migration and judge each step?Engineering systems
If a micro-app fails at startup, users cannot access other modules. How would you isolate the failure and, if needed, disable noncritical features to keep the rest available?Engineering systems
Several child apps depend on different React and component-library versions, causing both duplicate downloads and runtime conflicts. How would you govern shared dependencies?Engineering systems
Several child apps share the browser address bar, but back/forward, deep links, and login redirects behave inconsistently. How would you define a routing contract?Engineering systems
How would you design an article editing and publishing system? How should state and data be organized for drafts, review, scheduled publishing, multi-channel distribution, and edits after publication?System design
From a file or the network to picture and sound playing, what stages does a video go through? How do decoding, audio-video sync, stutter, and hardware acceleration each affect the experience?Computer-science foundations
How would you design an online audio or video editor? How should the timeline, assets, non-destructive editing, preview, and final export each be designed?System design
How would you design a document system for real-time multi-user editing? When several people edit the same passage at once, how do you guarantee eventual consistency, and how do you merge after offline edits?System design
How would you design a product where a person and an AI write together? How are the AI's edits shown, accepted, or rejected, and how are conflicts handled when both edit at once?System design
How would you design an immersive audio and video feed so that swiping up and down has almost no waiting? How do you balance preloading, player reuse, memory, and data?System design
Design a collaboration product that supports large-file uploads with resumability, where files must be validated and scanned before other members can access them. What constraints would you clarify, and how would you design upload, temporary storage, scanning, publication, permissions, and cleanup boundaries?System design
To build an online editor like Doc, PPT, or PS, how do you design the core data model and rendering? How do you handle undo and redo, selection, and performance on large files?System design
How should the loading and request strategy of streaming media be designed so it starts fast and does not stall? How do you trade off segmenting, adaptive bitrate, preloading, and caching?System design
Implement a map with concurrent reads and writes, per-entry expiration, and expired-entry cleanup. How would you define expiration semantics, synchronization boundaries, and deterministic tests?Coding and abstraction
Implement an incremental UTF-8 log parser that receives chunks which may split multibyte characters, reorder fields, contain multiple records, or include an exceptionally long line. Define parser state, error recovery, and memory limits, then implement repeatable core logic.Coding and abstraction
A third-party SDK callback updates data, but the UI does not refresh; forcing a refresh causes duplicate updates. How would you identify the framework’s change-detection boundary and choose the right integration point?Coding and abstraction
After a list item changes from record A to record B, its input still contains A’s draft. How would you explain component identity, keys, and state reuse, and choose where to fix it?Coding and abstraction
A custom dialog works with a mouse, but keyboard users cannot reliably enter, close, or return from it. Which focus-management behaviors would you inspect, and how would you verify a fix?Coding and abstraction
After an update, some users occasionally load new HTML with old JavaScript and the page fails. How would you design asset naming, cache policies, and release order to reduce inconsistency?Engineering systems
A search field briefly freezes after typing even though the network request completes quickly. How would you use the event loop, task queues, and main-thread occupancy to explain it and locate long tasks?Computer-science foundations
A page has valid server-rendered HTML, but content flickers after hydration and the console reports a warning. How would you locate the difference between server and client rendering?Debugging
Scrolling a list lowers frame rate, and the performance trace repeatedly shows layout work. How would you determine whether code is causing layout thrashing, and why does DOM read/write order matter?Computer-science foundations
The page HTML arrives quickly, but users still wait a long time to see the main content. How would you trace blockers across resource discovery, download, parsing, execution, and painting?System design
Design a reusable virtualized list: it renders only visible rows, but selection state must not leak to different data when DOM nodes are recycled. How would you define the interface and test it?Coding and abstraction
Different teams own creation, editing, and review, and their form feedback is becoming inconsistent. How would you decide which patterns to standardize and which to keep distinct? How would you check loading, empty, error, and recovery states?System design
Teams are copying shared components and adding local variants, making similar features inconsistent. How would you decide which differences belong in the shared design system and which should remain team-specific? How would teams help maintain those rules?Engineering systems
A feature works on the corporate network and most home networks, but requests often time out on a particular carrier or under poor connectivity; server error rates do not rise at the same time. How would you isolate causes across client, network path, protocol, and retry behavior?Debugging
The default locale renders correctly, but a few buttons overflow and tables shift after switching languages; failures occur only on narrow screens with enlarged system text. How would you narrow the cause and build regression coverage?Debugging
Teams can release micro-frontend modules independently, but loading, navigation, error messages, and accessibility behavior are becoming inconsistent. How would you decide which capabilities belong to the platform and which stay with product teams?Engineering systems
Several product teams override shared component styles with CSS, causing frequent regressions after upgrades. How would you choose between adding configuration, splitting the component, or keeping exceptions?Coding and abstraction

C · Value judgment and direction setting1

Brand asks for low-contrast text, but users with low vision struggle to read it; increasing contrast changes the brand presentation. How would you make and validate the design decision?Product judgment