What mattered
Missing interface knowledge had to become working middleware.
The retail operation depended on interfaces connecting point-of-sale and head-office systems. Without reliable information from the outgoing supplier, continuing the integration meant confronting a gap in understanding at a critical system boundary.
I worked with the business to understand its requirements, recovered the missing information by reverse engineering the existing interfaces, then designed and wrote software that translated data from the old head-office systems into Retail-J XML for the new EPOS system.
Why I mention it
Recovery continued through delivery and testing.
The middleware allowed the new and old EPOS systems to operate against the established head-office systems while preserving the functionality the business already depended on. I also supported the test team with technical questions about data and communications.
That is directly relevant when a business, agency or replacement supplier inherits an interface it did not build but must now understand, replace and prove safely.