Event management for professional organizers
This is an online congress registration application that helps organizers set up their registration pages and to manage the abstract submission and review process. On peak days it handles thousands of registrations per hour. A resilient infrastructure provides the required uptime.
When I joined this project, the codebase was an absolute mess without any quality insurance. New critical bugs arrived every day and old bugs reappeared regularly. By implementing a strict unit testing regime and combining the implementation of feature requests with the refactoring of critical parts, quality slowly improved. The net result was a vastly improved relation between the customer and my employer.