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…