Building a SaaS solo while working full-time… the real bottleneck isn’t what I expected

I’m building my first SaaS on the side while working full-time as a GTM Engineer

and I thought the hardest part would be:

coding
AI
or getting users

It’s not.

The real bottleneck is this:

You can’t simulate real usage.

I’m building a tool tryconfi.com that gives real-time coaching during sales calls.

On paper, everything worked.

In testing, everything worked.

Even in controlled calls… it worked.

Then I used it on an actual call during my job.

And immediately found a problem I would have never caught otherwise.

As soon as a third person joined the call, everything broke.

The system started confusing who the “prospect” was
and began giving completely wrong prompts.

Not slightly off.

Completely useless.

And the frustrating part?

There was no way I could’ve discovered that
without using it in a real, high-stakes environment.

That’s been the biggest challenge building solo:

You don’t have:

• a team testing edge cases
• lots of users giving feedback
• multiple environments to validate against

You have… yourself.

So now my “development process” looks like:

build something
use it on a real call
watch it break
fix it
repeat

It’s slower than I expected.

But also way more honest.

One thing I’ve realized:

If your product depends on real-time behavior
you can’t rely on assumptions

You need real-world stress testing
or you’re building in a vacuum

Curious how other solo builders handle this

How are you validating real-world usage
without a team or a large user base?