Engineered a large-scale e-learning platform serving 100,000+ active users with 2M+ monthly API requests. Built and maintained 150+ RESTful APIs with JWT authentication, role-based access control, and third-party integrations including payment gateways. Key features include a skill assessment engine, mentor dashboard serving 800+ mentors, B2B contract management for 50,000+ clients, and automated workflows. Optimized SQL Server and PostgreSQL performance by 80% and maintained 99.9% uptime across 32+ microservices. Built using ASP.NET Core, Angular, Entity Framework, Docker, and CI/CD pipelines.