Backend System DesignSenior⏱ 60 min
Design a notification system
Design APIs and backend architecture for multi-channel notifications.
backendqueuenotificationreliability
Start 60 min session →Frontend System DesignSenior⏱ 45 min
Design a real-time analytics dashboard
Frontend architecture for a live SaaS metrics dashboard.
frontendreal-timeperformancewebsocket
Start 45 min session →Full-Stack ArchitectureSenior⏱ 90 min
Design an interview preparation platform
Full-stack subscription SaaS for engineers practicing interview skills.
fullstacksubscriptionauthpayments
Start 90 min session →Backend System DesignIntermediate⏱ 45 min
Design a URL shortener
High-throughput URL shortening and redirect service at 1B redirects/month.
backendcachingdatabaseanalytics
Start 45 min session →Frontend System DesignIntermediate⏱ 30 min
Design a file upload UI
Reusable drag-and-drop file upload component with chunked uploads and retry.
frontendcomponentuxperformance
Start 30 min session →Frontend System DesignSenior⏱ 45 min
Design a social news feed (Meta)
Infinite-scroll feed with real-time post updates, likes, and virtualized rendering.
frontendvirtualizationreal-timeinfinite-scroll+1 more
Start 45 min session →Frontend System DesignSenior⏱ 60 min
Design a real-time chat UI (Messenger / Slack)
Real-time messaging UI with typing indicators, read receipts, and optimistic sends.
frontendreal-timewebsocketoptimistic-ui+1 more
Start 60 min session →Frontend System DesignIntermediate⏱ 30 min
Design a search autocomplete UI (Google)
Accessible autocomplete with debouncing, result caching, and keyboard navigation.
frontendcomponentaccessibilityperformance+1 more
Start 30 min session →Frontend System DesignSenior⏱ 45 min
Design a video player component (Netflix / YouTube)
Adaptive streaming video player with buffer states, quality selection, and accessibility.
frontendcomponentperformancestreaming+1 more
Start 45 min session →Frontend System DesignSenior⏱ 60 min
Design a collaborative document editor (Google Docs)
Real-time multi-user text editor with live cursors, conflict resolution, and offline support.
frontendreal-timecrdtoffline+1 more
Start 60 min session →Frontend System DesignIntermediate⏱ 30 min
Design a shopping cart UI (Amazon)
Persistent shopping cart with optimistic updates, offline support, and cross-tab sync.
frontendstate-managementofflineoptimistic-ui+1 more
Start 30 min session →Frontend System DesignSenior⏱ 45 min
Design a live map with real-time tracking (Uber)
Real-time driver position tracking on a map with smooth interpolation and state management.
frontendreal-timemapswebsocket+1 more
Start 45 min session →Frontend System DesignSenior⏱ 60 min
Design a drag-and-drop dashboard builder (Microsoft / Notion)
Widget-based dashboard where users drag, resize, and reorder components with layout persistence.
frontenddrag-and-dropcomponent-systemstate-management+1 more
Start 60 min session →Frontend System DesignIntermediate⏱ 45 min
Design a multi-step checkout flow (Shopify / Stripe)
Step-based checkout with form validation, payment integration, and resilient state management.
frontendformsstate-machinepayments+1 more
Start 45 min session →Frontend System DesignIntermediate⏱ 30 min
Design a photo grid with lazy loading (Instagram / Pinterest)
Masonry or fixed-grid image feed with virtualization, lazy loading, and a lightbox viewer.
frontendperformancevirtualizationlazy-loading+1 more
Start 30 min session →Frontend System DesignIntermediate⏱ 30 min
Design a notification center (Slack / Gmail)
In-app notification bell, real-time toast queue, badge counts, and persistent notification history.
frontendreal-timecomponentstate-management+1 more
Start 30 min session →Frontend System DesignSenior⏱ 60 min
Design an infinite canvas for a design tool (Figma / Miro)
Pan-and-zoom infinite canvas with virtualized object rendering, selection, and real-time collaboration.
frontendcanvasperformancereal-time+1 more
Start 60 min session →Full-Stack ArchitectureBeginner⏱ 60 min
Design a job application tracker
Full-stack app for tracking job applications, interviews, and offers.
fullstackcrudnotificationspermissions
Start 60 min session →Backend System DesignSenior⏱ 60 min
Design a video thumbnail A/B testing system
Build a pipeline to A/B test video frames and automatically select optimal thumbnails.
backendvideoa/b-testingpipeline+1 more
Start 60 min session →Backend System DesignIntermediate⏱ 45 min
Design a game scoreboard server
Scalable leaderboard supporting score submissions, top-100 queries, and per-player rank lookups.
backendleaderboardcachingredis+1 more
Start 45 min session →Full-Stack ArchitectureIntermediate⏱ 45 min
Design an international news app with IP-based localization
Detect user country via IP and serve localized news — identify problems and improvements.
fullstacklocalizationcdnip-detection+1 more
Start 45 min session →Backend System DesignIntermediate⏱ 45 min
Design an internal text/code sharing tool — capacity planning
Estimate server count needed for storage and CPU load for an internal paste-sharing tool.
backendcapacity-planningstorageestimation+1 more
Start 45 min session →Full-Stack ArchitectureIntermediate⏱ 60 min
Design a medical appointment waitlist system
Notify waitlisted patients when appointments are cancelled and manage slot acceptance within a time window.
fullstacknotificationsqueuescheduling+1 more
Start 60 min session →Backend System DesignBeginner⏱ 30 min
Design a music streaming app — single vs multiple servers
Evaluate the tradeoffs of single-server vs multi-server architecture for a playlist streaming service.
backendscalabilityarchitectureload-balancing+1 more
Start 30 min session →Backend System DesignSenior⏱ 60 min
Design an arcade game card payment system at scale
Design a distributed payment system for 125,000 arcade machines using proprietary game cards.
backendpaymentsdistributedoffline+1 more
Start 60 min session →Backend System DesignIntermediate⏱ 45 min
Design query logging for a search engine — storage estimation
Identify what data to collect and estimate storage requirements for a year of search query logs.
backendloggingstorageestimation+1 more
Start 45 min session →Backend System DesignIntermediate⏱ 45 min
Design a public file storage system with deduplication
Identify problems with bytewise file comparison for deduplication and propose efficient alternatives.
backendfile-storagededuplicationhashing+1 more
Start 45 min session →Full-Stack ArchitectureBeginner⏱ 30 min
Design a password validation system
Identify issues with common password rules and propose a more effective validation strategy.
fullstacksecurityauthenticationvalidation+1 more
Start 30 min session →Full-Stack ArchitectureIntermediate⏱ 45 min
Design a meal logging app that scales after viral growth
Diagnose slowdowns in a nutrition tracking app that surged in popularity and propose scalability improvements.
fullstackscalingdatabasecaching+1 more
Start 45 min session →Full-Stack ArchitectureIntermediate⏱ 45 min
Design a global cultural events platform with IP-based localization
Critique a design that uses IP detection to serve local-language event listings and propose improvements.
fullstacklocalizationi18ncdn+1 more
Start 45 min session →Backend System DesignSenior⏱ 60 min
Design a mall and amusement park kiosk payment system
Design a scalable prepaid-card payment system for 150,000 interactive kiosks worldwide.
backendpaymentsdistributedoffline+1 more
Start 60 min session →Backend System DesignIntermediate⏱ 45 min
Design a competitive game scoring system under high load
Optimize a scoring system for a competitive online game that struggles under peak load during events.
backendleaderboardcachingscalability+1 more
Start 45 min session →Backend System DesignIntermediate⏱ 45 min
Design an application performance monitoring log storage system
Identify what data to collect and estimate storage for a year of performance metrics logs.
backendmonitoringloggingstorage+1 more
Start 45 min session →Full-Stack ArchitectureIntermediate⏱ 45 min
Design a recipe and shopping list app that scales for the restaurant industry
Diagnose performance issues and design a scalable architecture for a recipe app exploding in popularity.
fullstackscalingdatabasecaching+1 more
Start 45 min session →Backend System DesignIntermediate⏱ 45 min
Design a children's drawing animation app — minimize server farm cost
Design an architecture to minimize server costs for CPU-intensive character animation processing.
backendcdncachingcost-optimization+1 more
Start 45 min session →Backend System DesignSenior⏱ 60 min
Design a sports stats aggregation service resilient to third-party API outages
Redesign a sports statistics platform to minimize the impact of unreliable third-party data API outages.
backendresiliencecircuit-breakercaching+1 more
Start 60 min session →Backend System DesignSenior⏱ 60 min
Design a smart freezer migration from networked to autonomous microcontroller
Identify key considerations when porting smart appliance functionality from a networked computer to a low-cost embedded microcontroller.
backendembeddededge-computingresource-constraints+1 more
Start 60 min session →Backend System DesignSenior⏱ 60 min
Design a short video sharing app with TTL-based expiry
Estimate resource costs and design a scalable architecture for a viral 1-minute video sharing app.
backendvideostoragescalability+1 more
Start 60 min session →Backend System DesignBeginner⏱ 30 min
Design a podcast streaming app — single vs multi-server tradeoffs
Evaluate the advantages and disadvantages of a multi-server architecture for a topic-categorized podcast streaming platform.
backendscalabilityarchitecturecdn+1 more
Start 30 min session →Frontend System DesignSenior⏱ 45 min
Design a frontend data-fetching layer (Fetch API)
Build a robust HTTP client with caching, deduplication, and retry using the Fetch API.
fetch-apicachinghttpabort-controller+1 more
Start 45 min session →Frontend System DesignSenior⏱ 60 min
Design an offline-first PWA (Service Worker API)
Architecture for a PWA that works offline using Service Workers and caching strategies.
service-workerpwaofflinecache-api+2 more
Start 60 min session →Frontend System DesignIntermediate⏱ 45 min
Design an offline notes app with local-first sync (IndexedDB)
Local-first notes app using IndexedDB as the primary store with cloud backup.
indexeddblocal-firstsyncoffline+1 more
Start 45 min session →Frontend System DesignIntermediate⏱ 45 min
Design infinite scroll with lazy image loading (Intersection Observer)
Virtualized feed with lazy loading using Intersection Observer API.
intersection-observerlazy-loadingvirtualizationperformance+1 more
Start 45 min session →Frontend System DesignSenior⏱ 45 min
Design a browser spreadsheet with heavy computation (Web Workers)
Offload formula evaluation and large dataset processing to Web Workers.
web-workersperformancespreadsheetcomlink+1 more
Start 45 min session →Frontend System DesignSenior⏱ 60 min
Design a browser-based video call UI (WebRTC API)
Peer-to-peer video/audio calling UI using WebRTC, signaling server, and TURN.
webrtcpeer-connectionsignalingice+2 more
Start 60 min session →Frontend System DesignIntermediate⏱ 45 min
Design an in-browser audio player with visualizer (Web Audio API)
Audio playback pipeline with waveform visualization using the Web Audio API.
web-audio-apiaudio-contextanalyser-nodestreaming+1 more
Start 45 min session →Frontend System DesignSenior⏱ 60 min
Design a collaborative whiteboard (Canvas API)
Real-time multi-user drawing surface using Canvas API with sync and undo.
canvas-apireal-timecrdtundo-redo+2 more
Start 60 min session →Frontend System DesignIntermediate⏱ 30 min
Design cross-tab cart and auth sync (Broadcast Channel API)
Keep cart, auth state, and UI in sync across multiple browser tabs.
broadcast-channelshared-workerstorage-eventcross-tab+1 more
Start 30 min session →Frontend System DesignSenior⏱ 60 min
Design end-to-end encrypted notes in the browser (Web Crypto API)
Client-side encryption of notes using Web Crypto API so the server never sees plaintext.
web-cryptoaes-gcmrsa-oaepkey-derivation+2 more
Start 60 min session →Frontend System DesignIntermediate⏱ 45 min
Design a location-aware store locator (Geolocation API)
Store finder with live GPS position, map rendering, and distance sorting.
geolocation-apimapsgpspermissions-api+1 more
Start 45 min session →Frontend System DesignIntermediate⏱ 45 min
Design a browser-based file manager (File API + File System Access API)
File upload, preview, drag-and-drop processing, and local file system access.
file-apifile-system-accessdrag-and-dropresumable-upload+2 more
Start 45 min session →