In 2005 Comverse asked us to help maintain their current set of real time billing webservices.
To cut our teeth we were tasked with maintenance of the current real-time billing web services backend. We basically just had to fix existing bugs. I believe we were able to start coding and contributing the very first day on site and continued cleaning everything up over a 2 month period.
Since we were in maintenance mode we were not able to create anything new but we were able to stabilize their existing system, provide more code coverage in unit tests, and decrease the overall number of issues they were tracking.
The existing application was vb.net with an Oracle backend. This was our first foray into vb.net having come from a primarily C# background. Was basically the same good ole .NET framework with a different syntax.