When the bug is not a styling bug

There is a category of software where a mistake is an inconvenience. A misaligned button, a slow page, a typo in a tooltip. You fix it, you move on, nobody was hurt. Most of my career has not been in that category, and it changes how you write code.

I co-founded and led the engineering for Chemist2U, a pharmacy delivery platform. When you are moving medication to people who need it, a bug is not a styling bug. The wrong item, the wrong address, a delivery that silently fails: those have consequences that no amount of polish makes up for. You learn quickly that the boring parts, the validation and the audit trail and the "are you sure" before something irreversible, are not overhead. They are the product.

The same lesson in three domains

The pattern repeats anywhere the real world has rules with teeth.

In nutrition, a health rating that the standard defines precisely has to be computed precisely. I pulled that math out into its own tested library rather than scatter it through an app, because getting it wrong in a regulated product is a compliance problem, not a cosmetic one. The rule lives in one place and every surface gets the same answer.

In finance, money is handled in cents, never floats, and every imported bank row gets a deterministic fingerprint so re-importing the same statement can never double-count a payment. The fuzzy part, matching a transaction to the right loan, is allowed to be probabilistic. The arithmetic is not.

In each case the shape is the same: find the part that must be exact, make it exact and testable and impossible to skip, and only then let the convenient, fuzzy, AI-assisted layer sit on top of it.

Correctness is a feature you cannot see

The hard thing about this kind of software is that the work nobody notices is the work that matters most. A delivery that just arrives, a rating that is simply right, a reconciliation that quietly balances. There is no screenshot for "did not ship the wrong medication." But that is the whole job, and once you have built in a domain where the stakes are real, it is hard to go back to treating correctness as optional.