Hiring the fourth engineer.
When you have three engineers, the fourth hire is the most consequential decision of the company. Here's how I'd run it again.
The fourth engineer at a company is doing something different from the first three. The first three are the founding team. The fourth is the first hire who didn't sign up to start a company. They signed up to work at this one.
This changes the math.
The thing nobody tells you
The first three engineers can absorb a bad hire. They've absorbed worse — they're founding the company. The fourth hire sets the cultural temperature for everyone who comes next. If you bring on someone who's brilliant and unkind, your seventh engineer is going to be brilliant and unkind, because that's the bar they were interviewed against.
Pick the fourth engineer not for the work they'll do next quarter, but for the engineer you want them to be in eighteen months — and the engineers they'll attract.
I made this mistake at my first company. We hired the strongest IC we could find for engineer four. Six months later, we'd built a culture that valued performative debate, and we couldn't hire anyone who didn't enjoy that. We'd shaped the next year of hiring without meaning to.
What I'd do now
Hire someone who's deeply good at the work but, more importantly, deeply good to work with. Skill is a floor, not a ceiling. The fourth engineer is going to onboard everyone who comes next. The question is whether you trust them to do that.
I'd also let the rest of the engineering team — the three of them — veto. Founders can't be the only ones screening for fit, because the founders won't be the only ones working with the hire.
Mei-Lin is a founding engineer at Orbital, where she works on developer ergonomics for AI tooling. She writes about hiring, ownership, and the early-stage trade-offs nobody warns you about.