What actually counts as validation
Sign-ups aren't proof and interest isn't proof. Here's the test I use now, and what it looked like when I applied it to my own product.
Product designer · Budapest
You don't have to quit your job to build something that's yours.
10+ years designing and building software products. I still do it for clients, and now I'm shipping and selling my own products after hours.
- 01
Sold a piece of custom software for €40,000. Rebuilt it alone in seven days.
- 02
Ran a studio of nine for five years. 37 client projects.
- 03
Lost more than €20,000 on a product nobody wanted.
The build notesFree
What I decide and why, what it costs, and what actually moves the numbers.
One click to leave. I don't send anything else.
01 / Who this is for
Who this is for, and who it isn't.
This is for you if
You've already tried to build something, either for yourself or for someone else.
You earn well from the day job. You're not looking for fast money. You want to build something you own.
You have 10–15 hours a week. Not 40.
You've started things in the last few years and none of them shipped.
This isn't for you if
You're starting from zero and need the fundamentals.
You want a tutorial you can copy without deciding anything yourself.
You're looking for a side hustle that pays next month.
What's missing isn't skill. You already know how to build. What's missing is judgment on your own project: what to build, what to leave out, when to ship it, and how to sell it.
02 / Why me
Three things that cost me real money.
01
I sold a piece of custom software for €40,000.
I spent five years running a studio, building software for clients of all shapes and sizes. We worked on large projects with teams of developers, and much smaller ones where the challenge was simply getting the right thing built.
As an experiment, I took one of those smaller projects. We had sold it to a client for €40,000. I rebuilt it on my own, using AI, in seven days.
I wasn't trying to prove that AI could replace a development team. I wanted to see how far the industry had moved, and how quickly a relatively small product or custom solution could now be built and shipped.
02
I know what a team of nine actually costs.
I know what it costs to build software properly, what a team actually spends its time on, and how much of that work AI can now absorb. I also know what it can't.
03
In 2023 I lost more than €20,000 building for a law nobody enforced.
A change in the law made proper whistleblowing systems mandatory for companies above a certain size. We did it by the book: researched the market, studied the competition, built the business case, and built the product. We even sold a few multi-year subscriptions before the law came into effect.
Then nobody enforced it. No fines, no pressure, and the companies that had been about to act simply didn't.
We had validated the demand. We never thought to validate the reason behind it.
I still design and build software for clients every week. This isn't a story about what I used to do.
The longer version →03 / What I'm building right now
DIY Wedding
It started at an AI launch-day competition in Budapest in June 2026. We started building at 9am. By 3pm, the cost estimator and landing page were ready, and I shared the waitlist in a few relevant groups. By 6pm, I was pitching the product in the final.
The waitlist brought 124 signups that day. Sixty of them became test users, and the feature list came from them, not from me.
It's live now. One-off price per wedding, no subscription. I'm figuring out the marketing in public, including the parts I get wrong.
124 signups day one60+ test usersBuilt solo
Budapest · June 2026 · pitching at 6pm
04 / Guides
The parts that don't change.
All guides →Validation, planning, and how to describe a product clearly enough that AI can actually build it. Nothing is locked, and you don't have to start at the beginning.
Why AI shouldn't build your software in one go
Your 20-page document will fit, and the AI will build something. The problem is everything it decides for you along the way, and what that costs you later.