The Contoso Convergence, Episode 12: The Customization Nobody Remembers
An Advanced Dungeons & Dynamics 365 session. Episode 12 of 14.
Previously on: Episode 11, Character Sheets, Denise’s caution turned out to be expertise nobody had asked about, and Vex offered to dig into the field she’d learned to distrust, the one that was wrong about one time in six.
Two weeks to go live. Everything on the ledger side finally looks green. This episode, that calm gets interrupted by something nobody was even looking for.
The Session
Vex: (deep in the code) Found something. There’s an override on tax calc. It only fires on international orders.
Thorne: Since when?
Vex: Git blame says two years ago. Author’s account is deactivated.
Sable: Do we know why it exists?
Vex: No comments. No ticket reference. Just a hardcoded exception for a specific country tax code.
Ai. Cassiopeia: I searched historical support tickets. There is a closed ticket from that period referencing an audit finding. No resolution notes attached.
Marge: Two weeks to go live and we’ve found a silent override to statutory tax logic with no documentation and no author.
Thorne: We can’t ship blind on tax. Not this close to the finish line, not this category.
Vex: I can reverse engineer what it’s compensating for. Give me two days.
Vex disappears into the code for the better part of the next two days, surfacing occasionally for coffee and increasingly specific questions.
Vex: (day one, afternoon) This override is doing something very deliberate. It’s not sloppy code. Whoever wrote this understood the tax engine at a level most consultants never bother to reach.
Sable: That’s not reassuring. That’s more unsettling.
Vex: (day two, morning) I think I found the audit finding it was responding to. There’s a gap between how the platform’s native tax engine handled a specific cross border scenario two years ago, and how the actual tax authority required it to be handled. Someone found that gap during an audit, panicked, and built this override to close it fast.
Thorne: Did it work?
Vex: (pulling up a comparison, going quiet) I need another hour before I answer that honestly.
Two days later, Vex has the answer, and it’s not what anyone expected.
Vex: The platform fixed the underlying bug in an update about eighteen months ago. This override is still running. On top of the fix.
The patch that outlived the problem it solved
An override built under audit pressure, with no documentation and a deactivated author, is exactly the kind of artifact that should terrify anyone doing a go live readiness review. But the actual failure here isn’t the override’s existence. Overrides built in a hurry, in response to a real and urgent finding, happen constantly, and they’re often the right call in the moment. The failure is that nobody built in a mechanism to revisit it once the underlying platform caught up.
That’s a subtly different problem than most of what the party has found so far. The shadow ledger, the TEMP dimension, the silent integration, all of those were things nobody built correctly the first time. This one was built correctly, for the moment it was built in, by someone who clearly understood the tax engine well enough to solve a genuinely hard problem under real pressure. The failure happened later, quietly, when the platform vendor shipped a fix and nothing in Contoso’s environment ever checked whether the original workaround was still needed.
This is the maintenance half of technical debt that almost nobody plans for. Everyone budgets for building the workaround. Almost nobody budgets for the moment, months or years later, when the reason for the workaround quietly disappears and the workaround itself doesn’t. A patch with no expiration date and no owner just keeps running, doing whatever it was built to do, whether or not that’s still the right thing to do.
What happens next
The platform fix and the old override are now both active, which means international tax has likely been calculated twice for a very long time. The party has two weeks to go live and a discovery that reaches back much further than two weeks, into territory that’s going to need more than an engineering fix.
Next episode: Episode 13, The Audit Trail (coming soon)
If your environment has a workaround built in response to a problem that might already be solved somewhere upstream, this episode is worth sitting with. Gamifying the Enterprise: Game Mechanics for Continuous Proficiency is available now on Amazon: https://www.amazon.com/dp/B0GY3VWLVX
And if you want a framework built around giving every workaround an owner and an expiration date, start here: adnd365.com/start
A Tinkerers Notebook 