Software developer · Wrocław, Poland
Wojciech Jastrzębowski
I’m a software developer on mainframe systems. With my team I build and maintain the application that runs payroll for the German market every month.
What a mainframe is
A mainframe is a computer built for one thing: to run an enormous number of operations inside a fixed window of time and get none of them wrong. Payroll for a few hundred thousand people has to finish overnight, because in the morning those people look at their accounts.
The code doing it is often older than I am, and it still runs. It does not get replaced, because the risk of a rewrite is real while the benefit is mostly aesthetic. Systems like this are invisible by design, and most people learn they exist only on the day one of them stops.
“We have no need of other worlds. We need mirrors.”
Technologies and tools
- COBOL
- JCL
- IBM z/OS
- TSO
- IOF
- Batch
- Payroll
- Debug
- SQL
- C#
- Agile
- SCRUM
- Azure DevOps
How I work
“Attention is the rarest and purest form of generosity.”
Payroll is as much regulation as it is code. Before the first line gets written, somebody has to work out what the law requires, what the client expects, and what to do where those two disagree. That part of the job, reading requirements, asking until the answer is unambiguous and turning it into something a machine can execute, takes no less of my time than the writing does.
I try to hold both sides at once: the practical one, how the system actually behaves, and the theoretical one, why a regulation reads the way it does. Practice on its own lasts exactly until the first exception to the rule.