Often I remember I want to make it just a piece better, and better, and better… it feels so good to give your little baby an extra polish.
“You never know boss, maybe the customer needs a second contact form later on, so let me do that generic form wrapper!” 🧑💻
We have so many excuses for that. But if we’re truly honest with ourselves — we know deep down that we ain’t gonna need that feature in the future, and all the extra money is burned. At least for the customer.
How to Think About It
A change of perspective is useful here. Would you like to watch someone burn your money on something you never ordered? I think the answer is clear.
The pattern plays out in code all the time:
// ❌ Building a "generic form system" before anyone asked for one
class FormBuilder {
constructor(config) {
/* ... */
}
addField(name, type, validators = []) {
/* ... */
}
addAsyncValidator(fn) {
/* ... */
}
render(container) {
/* ... */
}
}
// ✅ The ticket asked for a contact form — so write a contact form
document.querySelector("#contact-form").addEventListener("submit", e => {
e.preventDefault();
sendContactEmail(new FormData(e.target));
});The FormBuilder is satisfying to write. It’s also three days of work nobody requested, with a test surface nobody will maintain.
Reasons Not to Follow YAGNI
Distinguish Between Functional and Modular Code
Keep in mind that this rule of thumb is always about functions and templates, not about structure. It’s not telling you to stop creating classes or modules. If you want to build a factory for your different product types, go ahead — that’s sensible design, not premature speculation.
But We’ll Really Need It Later
Sometimes you genuinely know that taking the easy route now will cost more later. That’s worth a conversation with the product owner. Even if the upfront investment is higher, the client may prefer to build a prototype first — this is precisely the case with an MVP (minimum viable product).
The key word is know. If you’re speculating, it’s YAGNI. If you have a roadmap item, a written requirement, or a concrete deadline — that’s a different conversation entirely.
What’s the most elaborate “just in case” feature you’ve seen built that never got used? I’d love to hear it.