Practice series
Storage, media & content delivery
Uploads, sync, object storage, CDN delivery, transcode pipelines, and file metadata.
- 01Free
Ad Click Aggregator
Design an ad click aggregation system that ingests millions of click events per second and serves near-real-time plus historical aggregate metrics to advertiser...
Meta - 02Preview
Chat App
Design the client-side architecture of a WhatsApp-style mobile messenger — connection handling, message state, offline storage, and encryption all have to survi...
Discord - 03Preview
Chat Service
Design the backend infrastructure behind a chat product — stateful connection servers, message storage, and group fan-out — for hundreds of millions of concurre...
Discord - 04Free
Dropbox
Design Dropbox — a cloud file storage and synchronization service where users upload large files and keep them in sync across devices and shared folders.
Dropbox - 05Preview
Google Drive
Design Google Drive as a permissioned file platform — folder hierarchies, shared drives, and access control that scale across billions of files and third-party...
Google - 06Preview
Metric Monitoring and Alerting
Design the metrics pipeline behind a monitoring platform — the path from an SDK on thousands of hosts emitting numeric measurements, through streaming pre-aggre...
Uber - 07Preview
Monitoring and Alerting
Design the alerting and observability layer of a monitoring platform — the system that evaluates rules against incoming signals, decides who gets paged, and kee...
Practice bank - 08Preview
Netflix
Design Netflix’s video delivery system — stream a licensed, curated catalog to tens of millions of concurrent viewers worldwide with minimal buffering and consi...
Netflix - 09Preview
Recommendation System
Design a large-scale personalized recommendation system for feed/video/ads.
Netflix / Meta - 10Preview
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 - 11Preview
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 - 12Free
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 - 13Free
Web Crawler
Design a web-scale crawler that politely fetches and indexes billions of pages, deduplicates content, and keeps the corpus fresh.
Google - 14Preview
YouTube
Design YouTube’s upload and processing pipeline — accept massive volumes of user-generated video uploads and transform them into a playable, multi-resolution ca...
YouTube - 15Free
- 16Free
LLM Inference Gateway
Design an LLM inference gateway that sits between internal product teams and multiple model providers/backends, handling routing, streaming, quotas, and safety...
OpenAI / Anthropic - 17Preview
Vector Database
Design the storage and query engine of a vector database that indexes billions of embeddings for approximate nearest-neighbor search.
Meta (Faiss) - 18Preview
Fraud Detection
Design a real-time ML fraud/risk scoring system that scores payment transactions in under 100 ms.
Stripe - 19Preview
Object Storage
Design an S3-like object storage service that stores billions of immutable blobs durably and cheaply.
Amazon / Backblaze