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.

Content models, drafts vs. published, and admin panels that stay maintainable as the site grows.

The trade-offs between flat-file JSON and database storage for content management systems.

Separating content from presentation with API-driven CMS for multi-channel delivery.

Design permissions that editors, reviewers, and admins can work with safely.