I built my 4th SaaS in 2 weeks, part-time

I already own 3 SaaS products.
I’m past the stage where I can personally check every new signup.

But recently, while digging into user data, I realized a few whales had signed up for one of my tools… and I completely missed them.
No personal outreach. No follow-up. Just lost opportunities.

That’s when I decided to build my next micro-SaaS.

A simple service with an API that receives signups, enriches them automatically, and notifies me when a high-value user joins.

I called it WhoSignup.

How I built it:

I have 20 years of dev experience and I know what a real SaaS needs:
Authentication, rate limiting, email verification, payments, background jobs, logging, and security hardening… all those invisible things that make a product truly usable.

That experience helped me guide the AI properly.

I built WhoSignup with Lovable, an AI-powered app builder.
And instead of prompting for “code,” I treated it like a teammate.

Whenever I wanted to add something, I’d say:

“I want to add this feature. What’s your suggestion for implementing it?”

It would explain trade-offs, outline an implementation plan, and propose a clean solution.
Sometimes I’d even ask ChatGPT for more context before deciding which path made the most sense.
Then I’d tell Lovable:

“Okay, implement it this way.”

That loop worked incredibly well.

Example of that workflow:

• I noticed there was no email validation → I asked the AI to add it.
• I wanted a CAPTCHA on the signup form → I asked it to implement Cloudflare Turnstile.
• I wondered how to enrich signups → it proposed background processing with enrichment status fields and async edge functions.
• I wanted to check security → Lovable ran a scan, listed the issues, and fixed them automatically.
  It really felt like managing a junior dev who can code, test, secure, and deploy instantly.

What it built (in 2 weeks, part-time):

• Auth: signup, login, password reset, email verification
• Dashboard: API key, endpoint, cURL example, table of signups
  REST API with RLS and rate limiting
• Background enrichment (email + company data)
• Notifications based on Domain Authority + company size
• Email alerts via Resend from my own domain
• CAPTCHA protection (Cloudflare Turnstile)
• Stripe payments already integrated and working
• Automatic security scanning and fixes

I didn’t touch any infrastructure manually : everything was handled by AI or Lovable’s backend.

What surprised me most:

It wasn’t just “AI writes code.”
It was “AI acts like a founding engineer.”

I described what I wanted.
It built the schema, wrote migrations, handled authentication, built the UI, and debugged live issues when I tested things.

When I asked why something was done a certain way, it explained it — often with reasoning you’d expect from a senior engineer.

What I learned:

Describe intent, not code. Let AI translate ideas into implementation.
Treat AI like a teammate, not a tool. Ask questions, discuss trade-offs, then decide.
Ask for audits. It will catch issues before users do.
Iterate live. Test, break, fix — in minutes, not days.
Solve your own problems first. That’s where the best micro-SaaS ideas come from.

Where it stands

WhoSignup is live, stable, and already usable by others. Stripe integration is in place and fully tested. The app can start charging users anytime.
It enriches signups, filters noise, and emails me when a real company signs up.

It’s my 4th SaaS, but the first one built with AI instead of by me.
It took 2 weeks, part-time.

You can try it at https://whosignup.com