I have a day job as a founding engineer. I also build things on nights and weekends — CoachMyChess, OfferPro, and BetterCapital before I wound it down.
People think the hard part of building solo is the code. It isn't.
The hard part is that you are everyone. Product manager. Designer. Engineer. The person who answers the support email at 11pm. There's nobody to hand the frontend to while you "focus on the backend." There is no backend team. There's you.
Here's what I've actually learned.
Your constraint is time, not elegance
Early on, I over-built. Beautiful abstractions for problems I didn't have yet. Flexible data models nobody asked for. As a solo builder, every hour you spend polishing something users can't see is an hour you didn't spend finding out what they need. Boring and shipped beats clever and someday.
Pick one thing to be hard
For OfferPro it's the PDF parsing. For CoachMyChess it's turning a messy game history into feedback a 7-year-old understands. Everything else — auth, billing, the dashboard — should be as dull and off-the-shelf as possible. You get one complexity budget. Spend it where the product actually lives.
Ship it in front of a real person, fast
My kids are my QA team — a 6th grader and a 3rd grader who will tell me, without mercy, when something is confusing. If a feature survives them, it's ready. You don't need a focus group. You need one honest user and the willingness to watch them get stuck.
Full-stack solo is messy, and that's fine
You'll break the API with a migration. You'll lose a day to CSS. You'll find a security hole in your own auth flow three months in. This is the tax. It's still faster than coordinating a team before you know what you're building.
The reward isn't that it's easy. It's that the whole loop — idea, build, ship, learn — lives in one head, and it moves as fast as you do.