User Activity Feed Low-Level Design: Event Ingestion, Fan-Out, and Personalized Ranking
User Activity Feed: Overview A user activity feed aggregates events from actors a user follows and surfaces them in reverse-chronological […]
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Recommendation Feedback Loop Low-Level Design: Implicit Signals, Click-Through Tracking, and Model Retraining
Recommendation Feedback Loop: Overview A recommendation system without a feedback loop becomes stale. The feedback loop closes the cycle: collect
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Graph Search System Low-Level Design: Traversal, Index Structures, and Social Graph Queries
Graph Search System: Overview A graph search system enables queries over a network of nodes and edges — users, connections,
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ML Feature Store Low-Level Design: Feature Ingestion, Online/Offline Serving, and Point-in-Time Correctness
{ “@context”: “https://schema.org”, “@type”: “FAQPage”, “mainEntity”: [ { “@type”: “Question”, “name”: “What is point-in-time correctness in a feature store?”, “acceptedAnswer”:
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ML Model Serving System Low-Level Design: Versioned Deployment, A/B Testing, Shadow Mode, and Monitoring
{ “@context”: “https://schema.org”, “@type”: “FAQPage”, “mainEntity”: [ { “@type”: “Question”, “name”: “How does champion-challenger traffic splitting work in model serving?”,
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A/B Experiment Platform Low-Level Design: Assignment, Holdout Groups, Metric Collection, and Statistical Analysis
{ “@context”: “https://schema.org”, “@type”: “FAQPage”, “mainEntity”: [ { “@type”: “Question”, “name”: “How does deterministic user assignment work in an A/B
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Database Schema Migration System Low-Level Design: Versioned Migrations, Zero-Downtime, and Rollback
Database Schema Migration System Low-Level Design A schema migration system manages the evolution of a database schema alongside application code.
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Data Lake Architecture Low-Level Design: Ingestion, Partitioning, Schema Registry, and Query Layer
Data Lake Architecture Low-Level Design A data lake is a centralized repository that stores structured and unstructured data at any
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Streaming ETL Pipeline Low-Level Design: Kafka Consumers, Transformations, Exactly-Once, and Dead Letters
Streaming ETL Pipeline Low-Level Design A streaming ETL pipeline continuously consumes events from a message broker, transforms them in real
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Load Balancer Low-Level Design: Algorithms, Health Checks, Session Affinity, and SSL Termination
Load Balancer Low-Level Design A load balancer distributes incoming network traffic across a pool of upstream servers, ensuring no single
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Database Connection Pool Low-Level Design: Pool Sizing, Checkout/Return, Overflow, and Health Validation
Database Connection Pool Low-Level Design A database connection pool maintains a set of pre-established connections to a database server, lending
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Query Optimizer Low-Level Design: Cost Estimation, Plan Selection, Index Recommendation, and Query Rewriting
Query Optimizer Low-Level Design A query optimizer transforms a parsed SQL query into an efficient execution plan. The optimizer evaluates
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Health Check Service Low-Level Design: Active Probing, Dependency Graph, and Alerting
A health check service continuously probes every service in a platform, aggregates results through a dependency graph, classifies health states,
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Secrets Management System Low-Level Design: Vault Storage, Dynamic Secrets, Rotation, and Audit
A secrets management system stores, distributes, and rotates sensitive credentials — database passwords, API keys, TLS certificates, and cloud credentials
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Audit Logging System Low-Level Design: Tamper-Evident Records, Structured Events, and Compliance Queries
An audit logging system records every significant action in a platform — who did what to which resource, when, and