Order state machines, idempotency, and reservation logic for a checkout that handles real payments.

Webhooks, idempotency keys, and reconciliation for robust payment gateway integration.

Modeling products, variants, categories, and attributes for a flexible, searchable catalog.

Prevent overselling with reservation patterns and consistent inventory across channels.

Model order lifecycles as explicit state machines to avoid impossible states and subtle bugs.

A solid relational schema for products, orders, customers, and payments with correct constraints.

Cache catalogs, pricing, and pages without serving stale prices or stock to customers.

Queueing, throttling, and cache-first patterns to survive sudden traffic spikes.

Vendor onboarding, split payments, and the data model behind a multi-vendor marketplace.