In 2019, while head of IT, I approved a migration design that converted customer article identifiers from text to numeric keys. Leading zeros appeared unnecessary to the proposed common representation. The rehearsal showed why that assumption was wrong: 1,240 source identifiers produced 1,192 unique keys. Forty-eight pairs, affecting 96 identifiers, collapsed into the same values. The other 1,144 identifiers were unaffected by that collision pattern.
My first response was to ask whether the source data needed cleaning. Operating colleagues demonstrated that the paired identifiers referred to distinct records and that the leading zeros were part of their identity. The migration had changed the meaning, rather than discovered a duplicate the business should remove. The technical team had followed the design I approved, so I could not fairly describe the problem as a developer's implementation mistake. We stopped the programme before production cutover.
We retained the original text identifiers, rebuilt the mapping and repeated the collision checks. The rework cost ₹36 lakh and delayed the programme by six weeks. The account makes no claim that the faulty mapping had already caused a hospital event; it was caught in rehearsal. Equally, detecting it before cutover did not make the design decision harmless to the programme. Colleagues had to redo work, and operating teams continued with the existing systems for longer than planned.
I changed how identifier transformations were reviewed, asking source owners to explain the identity convention before technical standardisation was approved. The result was a corrected mapping for the programme, not a declaration that every future integration would preserve meaning automatically. The leadership lesson was to recognise where my own preference for a simpler representation had outrun the business evidence. I wanted the case to retain the initial error, the challenge from operations and the cost of correction, rather than turn a migration rehearsal into an uncomplicated technology success.