A single mistake was costing $50/month, and it went unnoticed.

This week in the Product Lab Conversations Podcast, we talked about something I like to call the Complexity Tax.

I recently ran a Sentry Audit for a client at Cre8fast, and the interface looked fine, actually. Clean UI, smooth experience, users were not complaining. The product was working perfectly, or looked like it was.

So, we needed to find out

When I checked the backend logs, I found something interesting. The app was making the same external API call twice every time a user clicked a button.

That one tiny mistake was costing the founder about $50 every single month.

That’s $600 a year… for nothing.

I broke this down fully on the podcast on The Product Lab Conversations. If you want to hear the full story and context, you can check it out here: https://thosynpax.com/lab

But in this newsletter, I want to show you how I actually found it.

The truth is, this is becoming very common now.

We are building faster than ever using tools like Cursor, Claude, Antigravity, and others. At Cre8fast, this is how we maintain speed. But there’s a small problem most people don’t talk about.

AI does not always clean up after itself.

You ask it to update a feature, it writes new logic, but sometimes it leaves the old one behind. Everything still “works,” but now you have hidden processes running in the background.

I call this ghost code.

You don’t see it on the UI. Your users won’t complain (except that it wasn't working). But your system is slowly leaking money and performance.

So how do you actually find this?

I use a simple method, and it has two stages.

The first stage is often called the code pass.

Here, I give the AI access to the entire codebase and ask it to scan for issues. Things like redundant logic, unnecessary API calls, or broken conditions. This part is useful, but it’s not enough.

Because AI understands code… but it doesn’t fully understand intent.

The second stage is where things get interesting.

Instead of just reading code, I simulate real user behavior.

This is where I use Antigravity.

I had the AI create a dummy account, skip unnecessary steps like email verification for testing, and then log in immediately. While it was going through this flow, I instructed it to fix any issues it encountered in real time and keep moving.

Now here’s the trick.

When you watch the process closely, you start to notice patterns. Repeated calls, unnecessary steps, delays… that’s where the real problems show up.

That was exactly how I found the duplicate API call.

Not from the code directly… but from watching the system behave.

Most founders don’t do this.

They build, test the UI once or twice, and move on.

But if your product was built with AI, there is a very high chance something small is hiding in your system right now. Something that looks harmless but is quietly affecting your cost or performance.

So here’s something simple you can do this week.

Pick one part of your product. It could be your login flow, your signup process, or even your checkout. Don’t just look at the code. Walk through it like a real user; you can either do it yourself, or you can use tools like Antigravity.

If it's a web app, open up the browser console while you are doing this so you can see all logs while doing the walkthrough.

Pay attention to what happens behind the scenes.

You might be surprised by what you find.

If you want us to do this properly for you, you can book a Sentry Audit with Cre8fast, and we’ll help you clean things up.

And if you want to learn how to think this way, how to build and audit like an actual Product Architect, then you should join the next PASTE cohort.

See you in the next newsletter

Thosyn Pax Product Architect & Tech Educator