A fractional CTO is a senior technology leader who works for a company part-time and takes real ownership of its technical decisions: architecture, hiring, vendors and the roadmap's technical risks. It is the role between an advisor, who gives opinions, and a full-time CTO, who runs the whole technology function.
I'm Paolo Antonio Rossi (luduvigo). I don't sell CTO time: I'm founder and CEO of Gorilli in Milan, where we build our own AI and Web3 products. But I have been CTO or co-founder and CTO at five startups, Chief Product Officer at another and an advisor to a third, so I have seen the job from every distance: full-time, part-time, and from the outside. This is what I'd want a founder to know before hiring a fractional CTO.
The roles I'm drawing on
- Co-founder and CTO at Honula (Lisbon, 2016–2017), where I built the technology from day one.
- CTO at TalentQrunch (Netherlands, 2017–2018) and at MiMoto Smart Mobility, the first electric scooter sharing made in Italy (Milan, 2018–2019).
- Chief Product Officer at Betterly (Milan, 2019–2021).
- Co-founder and CTO at Mistho (Berlin, 2021–2022), building a European open payroll API.
- Advisor to PotPot (Milan, 2021–2023).
- CTO at Tide Protocol | Five Elements Labs (Milan, 2022–2024).
The full list is on my CV.
Fractional CTO vs full-time CTO vs advisor vs agency
| Option | Commitment | Owns technical decisions | Best when |
|---|---|---|---|
| Full-time CTO | Full-time, usually with equity | Yes, all of them | Technology is the product and there is a team to lead |
| Fractional CTO | Part-time, a few days a month | Yes, for an agreed scope | Real decisions to make, not yet a full-time role |
| Technical advisor | A few hours a month | No, gives opinions | The team can execute and needs a second opinion on hard calls |
| Development agency | Project-based | Only inside the project | The scope is clear and someone on your side can judge the work |
The line that matters is accountability. An advisor can tell you a plan is wrong. A CTO, fractional or not, can stop it.
What the job really is in the first months
From the founding-CTO roles, the work that mattered most early on was rarely code:
- Saying what not to build. Most early technical debt comes from building things the product didn't need yet.
- Choosing boring infrastructure. The fewer moving parts, the more of a small team's time goes into the product. On my CV I wrote it as a principle: keep the stack minimal.
- Hiring the first engineers. The first two or three engineers set the culture for the next twenty. This is the hardest thing to do part-time.
- Being the honest voice in the room. Founders hear a lot of optimism. Someone has to say when a deadline or an architecture won't hold.
What's different for AI startups
AI products add risks that a generalist may not own:
- Model dependency. Keeping the model behind a thin layer, so you can switch provider, is a technical decision with commercial consequences.
- Evaluation. You need a way to know whether outputs are good before customers tell you.
- Data and permissions. Agents act on real systems. Least privilege, human confirmation on irreversible actions and full logs are not optional; I wrote about this in Model Context Protocol (MCP) explained and The Stack Nobody Checked.
Signs you need a full-time CTO instead
- More than a handful of engineers need day-to-day direction.
- Technology is the main thing investors are buying.
- Decisions are waiting for "the next CTO day" more than once a week.
At that point a fractional arrangement slows you down, and the best fractional CTOs say so themselves.
FAQ
What is a fractional CTO? An experienced technology leader who works for a company part-time, taking ownership of technical decisions without being a full-time employee.
When does a startup need a fractional CTO? When there are real technical decisions to make but not yet enough work, or money, for a full-time CTO, or between one CTO leaving and the next arriving.
What is the difference between a fractional CTO and a technical advisor? An advisor gives opinions; a fractional CTO is accountable for decisions and usually manages the people doing the work.
Does an AI startup need a fractional CTO? Only if nobody on the founding team can own AI-specific risks: model choice, evaluation, data handling and agent permissions.
Do you work as a fractional CTO? No. I build Gorilli's own products in Milan; this is what I learned from being on both sides of the role.
If you found this useful, subscribe to my Substack.