Ingestion Flow A webhook ingestion service receives HTTP POST requests from third-party providers (Stripe, GitHub, Twilio) and delivers the events […]
Federation and Schema Ownership A GraphQL gateway unifies multiple microservice schemas into a single graph that clients query. Each service
gRPC Fundamentals gRPC uses HTTP/2 as its transport and Protocol Buffers as its serialization format. Compared to REST+JSON: strongly typed
Connection Lifecycle WebSocket connections begin as HTTP requests and upgrade to a persistent bidirectional channel: Client sends HTTP GET with
Quota Management Service: Low-Level Design A quota management service defines resource limits per customer or user, tracks real-time usage against
A/B Test Assignment Service: Low-Level Design An A/B test assignment service determines which experiment variant a user sees and guarantees
Holdout Group Service: Low-Level Design A holdout group service maintains a permanently withheld cohort of users who never receive new
Experiment Logging Service: Low-Level Design The experiment logging service collects exposure and conversion events, computes metric values per variant, runs
Clickstream Analytics Pipeline: Low-Level Design A clickstream analytics pipeline captures every user interaction on a web or mobile product, processes
User Journey Tracker: Low-Level Design A user journey tracker records every touchpoint across devices and channels, resolves them to a
What Faceted Search Is Faceted search lets users progressively narrow results using multiple independent filter dimensions — category, price range,
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
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,
