What it was
My first industry role after graduating, as a software developer at HST Consulting in Addis Ababa. I worked on the frontend of HST Payroll, a software-as-a-service HR and payroll product: the screens HR staff use day to day, form validation, and the calls into the REST APIs the backend team exposed. The work was JavaScript and HTML on the client side, Git for collaboration, and a lot of back and forth with backend developers about API contracts and error handling. It is a commercial product, so there is no public code to link here.
What I learned
Payroll is where small frontend mistakes become money mistakes, so I learned to treat validation and state as correctness problems rather than polish. Working against someone else's API taught me to read contracts carefully and to ask for them in writing, the same habit I later brought to data contracts between pipelines and their consumers. It also showed me that I cared more about the data behind the screens than the screens themselves, which pointed me towards data engineering.