• Product and system architecture
• Mobile, web, backend, and database decisions
• Authentication, MFA, roles, and permissions
• Payment, card-provider, and third-party integrations
• Webhooks, idempotency, refunds, and reconciliation
• Security, audit logs, observability, and operational controls
• Automated testing and production hardening
• Docker, CI/CD, AWS or GCP deployment
• Technical documentation and a roadmap your team can continue