Netflix System Design Questions

Design a Distributed Frequency-Capping Service

Design a frequency-capping service for an advertising platform. Advertisers set caps such as 'a user may see this ad, campaign or line item at most N times per rolling 24 hours or 7 days'. On each ad request (tens to hundreds of…

Also reported as: Design Ad Frequency and Order Tracking · Design Rolling-Window Ad Frequency Capping · Design ad frequency capping +2 more

Model ads demand data for reporting

Design the data model for an advertising platform: advertisers/accounts, campaigns with budgets and flight dates, ad groups or line items, creatives and assets, targeting criteria, and delivery and performance events. Cover the…

Also reported as: Model data for an ads platform · Design an ads data model

Design Publisher Configuration Rules

Design a configuration system for the supply side of an ad platform: publishers own many sites, apps and placements, and each needs custom rules (allowed ad categories, floor prices, frequency limits) with inheritance from…

Also reported as: Design config rollout and click aggregation

Design a Scheduler for ML Training and Batch Inference Jobs

Design a distributed job scheduler that runs user-defined jobs at a specified time (one-time) or on a recurring cron schedule, at a scale of millions of jobs per day. Requirements: jobs fire close to their scheduled time, each…

Design a File Backup System

Design a file (or photo) storage and sync service like Dropbox, Google Drive or iCloud Photos. Users upload files from one device and see them on all devices; they can share files and folders, keep versions, and work offline with…

Design an Ad Pacing System

Design an ad pacing system for a large video advertising platform. Advertisers create campaigns with budgets, start and end dates, targeting, and delivery goals (impressions or spend); the system must spread delivery smoothly…

Design homepage viewport rendering with deduplication

Design how a streaming app's homepage (like Netflix) renders rows of titles: fetch only the rows and items visible in the viewport (lazy loading as the user scrolls), and deduplicate titles so the same show does not appear in…

Design an ads audience targeting system

Design an audience targeting system for an ads platform. Advertisers define audiences (segments by demographics, interests, lists of user IDs, lookalikes), and at ad-serving time the system must decide within milliseconds which…

Design a crash-resilient file system

Design a file system abstraction: an in-memory hierarchical file system supporting mkdir, ls, create file, write/append, read and delete on paths; then discuss how to persist it so that file contents and metadata are recovered…

Design config rollout and click aggregation

Design an ad click and impression aggregation system. Ingest a high-volume stream of ad events ({ad_id, campaign_id, user_id, event_type, timestamp}, billions per day) and provide aggregated metrics (clicks, impressions, CTR per…