Experiment Logging Service: Low-Level Design The experiment logging service collects exposure and conversion events, computes metric values per variant, runs […]
A/B Test Assignment Service: Low-Level Design An A/B test assignment service determines which experiment variant a user sees and guarantees
User Journey Tracker: Low-Level Design A user journey tracker records every touchpoint across devices and channels, resolves them to a
Clickstream Analytics Pipeline: Low-Level Design A clickstream analytics pipeline captures every user interaction on a web or mobile product, processes
The Core Requirement Autocomplete must return the top-K relevant completions for a given prefix within 50ms p99 from the moment
The Inverted Index Full-text search is powered by an inverted index — a data structure that maps each unique term
What Faceted Search Is Faceted search lets users progressively narrow results using multiple independent filter dimensions — category, price range,
URL Scheme and Parameter Design A thumbnail service exposes a clean HTTP API for on-demand image transformation. The URL encodes
The Core Problem A follower feed must show a user the recent posts from everyone they follow, sorted by recency,
What KYC Is and Why It's Hard Know Your Customer (KYC) is the process by which a business verifies the
What Phone Verification Accomplishes Phone verification confirms that a user possesses a specific phone number at registration or for two-factor
What a Job Coordinator Solves A job coordinator manages the execution of complex multi-step workflows where tasks have dependencies on
Why Feature Toggles? Feature toggles (also called feature flags or feature switches) decouple code deployment from feature release. You ship
Why Centralize Configuration? Hardcoding configuration in application deployments creates operational problems: changing a timeout requires a redeploy, different environments diverge
Why Health Check Endpoints Matter A health check endpoint gives orchestration platforms and load balancers a programmatic way to know
