Practice series
Search, retrieval & ranking
Indexes, retrieval, autocomplete, recommendations, feeds, ranking, and RAG.
- 01Preview
Coupons and Deals Platform
Design a coupons and deals platform where users browse and search a large, frequently changing catalog of deals and redeem coupon codes exactly once per limit,...
Practice bank - 02Preview
Facebook Post Search
Design search over a social feed — let users find posts by keyword in near real time while respecting each post’s privacy/visibility settings.
Meta - 03Preview
Flight Booking System
Design a flight booking system that lets travelers search and book multi-leg itineraries across airlines, reserving fare-class seat inventory and issuing ticket...
Duffel - 04Preview
Game Leaderboard
Design a real-time game leaderboard that ranks millions of players by score, supports regional and time-windowed boards, and serves both top-N and a given playe...
Strava - 05Preview
Hotel Reservation (Booking.com)
Design Booking.com — a hotel marketplace aggregating live availability and pricing from thousands of independent supplier hotels, where search results must stay...
Booking.com - 06Preview
Hotel Reservation
Design a single-chain hotel reservation engine — travelers search date-range availability across properties, place a hold, and confirm a booking without ever ov...
Practice bank - 07Preview
Recommendation System
Design a large-scale personalized recommendation system for feed/video/ads.
Netflix / Meta - 08Preview
Search Bar Autocomplete
Design the autocomplete/typeahead system behind a search bar that returns the top-K query suggestions for a partial prefix within a sub-50ms budget, at the scal...
Meta - 09Preview
TikTok
Design TikTok’s For You feed — rank and serve an endless short-video feed personalized per user without relying on who they follow.
ByteDance - 10Free
Tinder
Design Tinder — a location-based dating app with swipe feeds, mutual-match detection, and recommendation of nearby profiles.
Tinder - 11Free
Top K Songs (Spotify)
Design Spotify's Top-K most-played songs feature — compute top charts over sliding time windows at listening-event scale.
Spotify / Meta - 12Preview
Yelp
Design Yelp — a local business search and review platform that returns nearby, filterable business results ranked by relevance and rating.
Yelp - 13Preview
RAG Knowledge Assistant
Design an enterprise RAG knowledge assistant that answers employee questions over internal documents (wikis, tickets, contracts) with grounded, cited answers wh...
OpenAI - 14Free
- 15Preview
- 16Preview
Vector Database
Design the storage and query engine of a vector database that indexes billions of embeddings for approximate nearest-neighbor search.
Meta (Faiss) - 17Preview
News Feed Ranking
Design the ranking system for a social news feed like Instagram or Facebook.
Meta (Instagram) - 18Preview
Visual / Multimodal Search
Design a visual and multimodal search system that retrieves visually similar images (and text-to-image matches) from a catalog of billions.
Pinterest