A case study says what was built. These say what was refused, and why — the choices that shaped the systems more than any feature did.
DEC/001
The counter was already taking devices in every day, and the records it produced were the only history the service desk had. A rewrite would have meant a day on which both were true at once: the old system no longer trusted, the new one not yet proven.
So the new system was built around the old one instead of over it — same records, new surfaces — until the point where switching off the original changed nothing anyone could feel.
DEC/002
The accounting database is old and it is not going anywhere: it is what the ledger, the tax record and years of history are written in. Moving it would have been a data project with no operational payoff.
It is read, not replaced. The flow runs one way — Firebird into the operational layer — so there is never a question about which copy is authoritative when the two disagree.
DEC/003
A store's network is not a promise. The shift still opens, the till is still counted and the customer is still standing there when the connection is not.
So the shop-floor tools are installed applications with a cached shell and an offline state, not pages that need a signal to render. The work is recorded locally and reconciled after, because the alternative is staff falling back to paper — and paper never arrives in the report.
DEC/004
Operations do not stop for a migration. Every system here was introduced next to the process it replaced and took over gradually, which means there was always a working path through the day.
It costs more — two systems to keep honest for a while — and it is the only version that has never needed a rollback.
DEC/005
The test for a feature is not whether someone asked for it. It is whether a manual step disappears the day it ships — a phone call, a second entry, a sheet someone was keeping on the side.
Features that only add a screen add maintenance and take attention from the floor. They get refused, and the request usually turns out to be a symptom of a step further upstream that should not exist either.