System Design Drill Day 15: Real-Time Chat and Live Order Tracking
How to design real-time chat and live tracking: polling vs SSE vs WebSockets, a Redis pub/sub backplane, sequence numbers and resync.
#interview-preparation
Posts tagged #interview-preparation
System Design Drill Day 14: URL Shortener and Unique ID Generation
How to design a URL shortener: base62 codes, ID generation strategies, 301 vs 302 redirects, Redis caching and async click analytics.
System Design Drill Day 13: Designing a Multi-Channel Notification System
How to design a notification service with per-channel workers, priority queues, preferences, dedup and signed webhook retries.
System Design Drill Day 12: The Saga Pattern for a Multi-Step Checkout
How sagas replace distributed transactions with local steps and compensations, using a multi-step checkout as the example.
System Design Drill Day 11: The Transactional Outbox Pattern
Why writing to the database and pushing to a queue can't be atomic, and how a transactional outbox fixes lost and phantom events.
System Design Drill Day 10: Circuit Breakers, Timeouts and Degradation
How circuit breakers, timeouts and bulkheads keep a checkout alive when the payment gateway or SMS provider starts failing.
