The Distributed Scheduler Problem A scheduler that runs on a single node is a single point of failure. A scheduler […]

What a Response Cache Does A response cache sits in front of upstream services and stores HTTP responses so that

What a Request Router Does A request router sits between clients and backend services, inspecting each incoming HTTP request and

Dependency Graph Construction An asset pipeline must understand the relationships between source files to build correctly. The dependency graph is

Promotion Schema A discount engine evaluates active promotions against a cart and computes the final discounted price. The promotion schema

Coupon Schema A coupon service manages promotional codes that apply discounts to orders. The core schema: CREATE TABLE coupons (

Core Schema The subscription manager tracks the relationship between users, plans, and billing periods. CREATE TABLE subscriptions ( subscription_id UUID

Preference Hierarchy A user preferences service must resolve the right value for any preference key given a user and device

URL Scheme An image optimization service accepts transform parameters via URL and returns a processed image. A clean URL scheme

Ingestion Flow A webhook ingestion service receives HTTP POST requests from third-party providers (Stripe, GitHub, Twilio) and delivers the events

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

Federation and Schema Ownership A GraphQL gateway unifies multiple microservice schemas into a single graph that clients query. Each service

Quota Management Service: Low-Level Design A quota management service defines resource limits per customer or user, tracks real-time usage against

Holdout Group Service: Low-Level Design A holdout group service maintains a permanently withheld cohort of users who never receive new