Token Bucket Rate Limiter Low-Level Design: Redis Implementation, Distributed Coordination, and Burst Handling
Overview A token bucket rate limiter controls how many requests a client can make within a time period while allowing […]
System Design
System Design
Price History System Low-Level Design: Time-Series Storage, Change Detection, and Alert Notifications
Overview A price history system records product price changes over time, enables historical chart queries, and fires alerts when a
System Design
Digest Email System Low-Level Design: Aggregation, Scheduling, Personalization, and Delivery
Overview A digest email system aggregates user-relevant events over a configurable time window and delivers a single summarized email rather
System Design
Tenant Isolation System Low-Level Design: Row-Level Security, Connection Pool Limits, and Noisy Neighbor Prevention
Tenant Isolation System: Low-Level Design A multi-tenant SaaS application serves many organizations (tenants) from a shared infrastructure. Tenant isolation ensures
System Design
Multi-Region Failover System Low-Level Design: Health Monitoring, Lag-Gated Promotion, and DNS-Based Traffic Cutover
Multi-Region Failover System: Low-Level Design A multi-region failover system routes traffic away from a failing region to a healthy standby,
System Design
Distributed Tracing System Low-Level Design: W3C Traceparent, Span Recording, Sampling, and Trace Visualization
Distributed Tracing System: Low-Level Design A distributed tracing system records the journey of a request as it propagates through multiple
System Design
Saga Orchestration System Low-Level Design: Distributed Transactions, Compensation, and Idempotent Step Execution
Saga Orchestration System: Low-Level Design A saga is a sequence of local transactions, each in a separate service, that together
System Design
Canary Deployment System Low-Level Design: Traffic Splitting, Guardrail Evaluation, and Automated Rollback
Canary Deployment System: Low-Level Design A canary deployment system routes a small fraction of production traffic to a new version
System Design
SLA Monitoring System Low-Level Design: Metric Ingestion, Threshold Evaluation, Alert Deduplication, and Uptime Calculation
SLA Monitoring System: Low-Level Design An SLA monitoring system tracks whether a service is meeting its availability, latency, and error
System Design
Activity Feed Aggregator Low-Level Design: Fan-Out Strategy, Celebrity Problem, Redis Sorted Sets, and Pagination
Activity Feed Aggregator: Low-Level Design An activity feed aggregator collects events from multiple services — post created, user followed, payment
System Design
Payment Refund System Low-Level Design: Double-Refund Prevention, Processor Integration, and Async Processing
Payment Refund System: Low-Level Design A payment refund system reverses a completed charge — partially or fully — and ensures
System Design
Webhook Subscription System Low-Level Design: Registration, Challenge Verification, Event Filtering, and SSRF Prevention
Webhook Subscription System: Low-Level Design A webhook subscription system lets external developers register URLs to receive event notifications. Unlike the
System Design
Email Unsubscribe System Low-Level Design: Category Preferences, One-Click RFC 8058, and CAN-SPAM Compliance
Email Unsubscribe System: Low-Level Design An email unsubscribe system lets users opt out of specific email categories while maintaining compliance
System Design
Invite System Low-Level Design: Token Generation, Link Invites, Redemption, and Race Condition Prevention
Invite System Low-Level Design An invite system lets existing users bring new members into a product — a workspace, a
System Design
Document Versioning System Low-Level Design: Snapshot-Delta Storage, Efficient Reconstruction, and Integrity Checks
Document Versioning System: Low-Level Design A document versioning system preserves every historical state of a document so users can view,