E-Commerce Order Platform

Summary

An e-commerce order lifecycle platform handling cart, checkout, payment, fulfillment, and returns across a mixed read/write workload where product discovery is read-heavy, checkout is write-transactional, and fulfillment is event-driven. The saga pattern orchestrates multi-step checkout: reserve inventory → charge payment → confirm order → notify fulfillment. PostgreSQL owns order records and inventory with row-level locking; Redis holds session state and cart contents with sub-millisecond access; RabbitMQ delivers fulfillment notifications with dead-letter handling; Elasticsearch serves product search and order history with faceted navigation. CQRS separates the write command path from the read model: the order read model is denormalized for fast order history queries without joining across domain tables.

Problem Statement

E-commerce platforms concentrate two fundamentally different operational problems in a single system: the read-heavy product discovery path (millions of product page views with low write rate) and the write-contention checkout path (flash sale events driving thousands of concurrent buyers at the same inventory rows simultaneously). A payment provider timeout during checkout must not leave inventory reserved and payment charged: the compensation path must be as reliable as the forward path. Order status updates must fan out to the customer app, warehouse system, and shipping provider without coupling checkout latency to downstream notification delivery. Return and refund flows invert the entire saga, requiring the same compensating transaction reliability in the reverse direction.