Category: System Design
Designing a Real-Time Cross-Sell & Upsell Recommendation Engine at Checkout
A production-grade system-design walkthrough for a real-time checkout cross-sell & upsell recommendation engine at ~1M requests/minute: two-speed architecture (fast cache-driven online path + async Kafka/Flink/warehouse/model-registry offline path), Recommendation Orchestrator with a hard 40 ms timeout budget and static fallback, three-layer caching (edge, in-proc LRU, Redis cluster), Rules Engine as final…
Designing a Subscription-Box E-Commerce System
A production-grade system-design walkthrough for subscription-box e-commerce: staggered recurring billing with idempotency keys, dunning with exponential backoff, preference-driven curation as constraint satisfaction, atomic optimistic inventory reservation, event-driven saga (billing → curation → fulfilment) over per-subscriber Kafka partitions, cutoff-aware APIs, PCI tokenisation at the gateway boundary, three-way reconciliation, and shadow →…
