What Is a Fractional CTO? (And When You Actually Need One)
A fractional CTO is not a junior hire or a part-time employee. Here's what they actually do, what it costs, and when a startup genuinely needs one versus when you're just avoiding a hard decision.
A fractional CTO is a senior technical leader who works with your company part-time — typically 4–16 hours a week — and owns the same decisions a full-time CTO would make: architecture, hiring, process, vendors, and technical strategy. Embedded in the team with real accountability for technical outcomes.
What they actually do
- Architecture decisions — Choosing the right database, API design, infrastructure provider, and making the calls that are expensive to undo later.
- Engineering hiring — Writing job specs, running technical screens, and helping avoid the mis-hires that set teams back months.
- Technical due diligence — Preparing your stack and your story for a fundraise, or reviewing another company's tech during an acquisition.
- AI adoption — Deciding where AI actually helps your product and where it introduces reliability, cost, or security problems nobody has thought through yet.
- Vendor decisions — Evaluating tools before you're locked in. AWS vs Fly.io. Supabase vs managed Postgres. Which AI model fits your latency and cost constraints.
- Engineering process — Pull requests, deployments, incident handling, on-call. The stuff that keeps velocity up and 3am pages down.
When you need one
- You're scaling past the founding team and have no technical co-founder to evaluate engineer candidates.
- Technical debt has accumulated and you don't know what's load-bearing versus what's safe to cut.
- You're going into a Series A and investors want to audit your technical choices.
- You're adopting AI tooling and need someone with real production experience — not someone who's read the marketing copy.
- Your engineers are good but nobody is making the hard architectural calls, so decisions keep getting deferred.
When you don't
If you already have a strong technical co-founder actively leading the team, you don't need this. If you're pre-product and still exploring, you need a builder, not a leader. If you want someone to manage a team full-time, that's a different hire.
What it costs
Typical range: €3,000–€8,000/month for a 4–8h/week retainer. Sprint engagements are fixed-price against a specific deliverable. A one-time technical audit is a single flat fee.
Compared to a full-time CTO — which runs €150,000–€250,000/year in salary and equity — a fractional arrangement delivers the same decision-making quality at a fraction of the cost, at a stage where full-time commitment often isn't the right fit anyway.