On our architecture diagram, two systems exchanged data through an integration. In reality there was a third component between them, and it was a workbook on a finance analyst's drive. Her part of the process took about forty minutes each month. Export a file from the first system, open the workbook, refresh a set of lookups, apply a rate, correct a category mapping that the source system had never been configured to produce, and upload the result into the second. She had built it eleven years ago when the project that was supposed to handle the mapping ran out of budget, and it worked, every month, without fail. Nobody in IT knew it existed, because nothing about it ever generated a ticket. We found out when she broke her wrist and the month end figures did not appear. What we then discovered is the ordinary catalogue of what happens when a business-critical step lives outside every system that IT manages. There was no version history, so we could not tell when the hard-coded rate had last been reviewed, and it had not been since 2021. There was no audit trail of who changed what, in a process feeding numbers that end up in a statutory return. The file was backed up only by her laptop's sync client, which had been paused since a disk warning. And the category mapping encoded business rules that existed nowhere else in writing, which meant the workbook was not just a tool but the only surviving specification of how two departments had agreed to classify things. The instinct in IT is to treat this as a governance failure by the business. I think that is the wrong reading. The spreadsheet existed because a real requirement was left unfunded and somebody solved it anyway rather than letting the month end fail. Blaming the person who kept the process running is a reliable way to ensure the next one stays hidden. We did the dull, correct sequence. Document what it does. Put it somewhere shared and versioned while it is still the live process. Then build the mapping properly, which took about nine days. Ask your finance and operations teams what they open every month. The answers are part of your estate whether or not they are on your diagram. – Serguey Shinder