Frontend System Design
The frontend design round — RADIO, the building blocks, and the prompts that keep coming up.
14 topics
Running a Frontend Design Interview
RADIO as a timeboxed structure for the 45 minutes, and the four things that separate a senior answer from a competent one.
core25 minFrontend API Design
Designing the contract from the client's side — payload shape, pagination, error envelopes, and the endpoints that stop a UI from making ten round trips.
core25 minMachine Coding Classics
The dozen components that get asked live in a shared editor, and what the interviewer is actually scoring in each.
core30 minDesign an Autocomplete
The canonical frontend design prompt — debounce, cancellation, out-of-order responses, caching, and a listbox that a keyboard can actually drive.
core25 minDesign an Infinite Feed
Cursor pagination, a normalised cache, virtualisation, and keeping scroll position stable when items shift underneath the user.
core30 minDesign a Data Grid Dashboard
Server-side sorting and filtering, URL-encoded view state, windowed rendering, and charts that don't block the main thread.
core30 minDesign a Multi-Step Form
Wizard state as a machine, validation on both sides, resumable drafts, and submitting exactly once.
core25 minDesign a File Uploader
Chunked, resumable uploads straight to object storage — with presigned URLs, concurrency limits, progress, and retries that survive a lift ride.
core30 minDesign a Notification System
The bell icon, the toast stack and the push permission — transport choice, unread counts across tabs, and not asking for permission on page load.
core25 minDesign a Chat Application
Optimistic sends with client-generated IDs, ordering and dedupe, reverse-scrolling history, and the streaming-LLM variant these companies actually ask.
core30 minDesign a Collaborative Editor
Two people typing in one document — why last-write-wins fails, what OT and CRDTs each cost, and the parts you can actually build in 45 minutes.
core30 minDesign an Analytics SDK
A third-party script on someone else's page — batching, `sendBeacon` on unload, a tiny bundle, and never breaking the host site.
core25 minFrontend Caching and Offline Architecture
The four caches a browser app actually has, how they interact, and what it takes to keep working without a network.
core30 minDesign a Design System
Tokens, component API contracts, versioning and adoption — the design prompt where the hard parts are organisational, not technical.
core30 min