Design and develop scalable SaaS systems, microservices, APIs, and complex features from conception through deployment. Leverage AWS serverless, event-driven, and container technologies while ensuring performance, reliability, observability, security, and compliance. Collaborate with architects, product managers, DevOps, and other engineers; participate in code reviews, testing, CI/CD, agile ceremonies, technical-debt reduction, and production support. Mentor engineers and contribute to architectural discussions and continuous engineering improvements.