Build, buy, or use AI?
Which parts of the product should be custom, which should be a vendor, and where AI actually helps. Get it wrong and the burn goes into the wrong things.
A fractional CTO with a team behind them
Diffco’s CTO and senior architects take on the decisions that shape your product: architecture, roadmap, vendors, hiring, and what not to build. When the plan says build, a senior engineering team is already in the room.
Advice that ends in working software, not a slide deck.
Products we developed are used by
Awards and client reviews
- Top AI Development Company
- Top 10 Software Developers
- Top AI Developers
in California
- Top Staff Augmentation Company
Diffco took on a complex financial system build for us — the kind of work that touches fund accounting and compliance, where there’s no margin for error — and they delivered. They helped us shape our AI product strategy rather than just executing tickets. Real ownership of the outcome.
Adam HooksCEO at Vero K12Their commitment to excellence ensures our platform remains robust and adaptable to our evolving needs. With their expertise, we've successfully enhanced our offerings, making our collaboration highly effective.
Pete GualfettiHead of Design and Integration at Good2GoWe were impressed by Diffco's approach to the development process and how they engineer new solutions. They look ahead, learn about your product and strategy, and develop sophisticated, highly functional solutions.
Stas TushinskiyCEO & Co-founder at InstreamaticDiffco supplied us with the skilled engineers we needed to meet our ambitious goals. Their account manager proactively addressed concerns, ensuring our expectations were met.
Razvan SpatariuSenior Software Engineering Manager at MultiverseDiffco handled discovery for two complex health tech AI products for us. They’re technically sharp, honest about what’s actually worth building, and easy to work with. They moved fast without cutting corners and understood the healthcare space. Highly recommend.
Mark MagazuPrincipal at M3 Veterinary Innovation AdvisorsDiffco's expertise and engineering approach increase the reliability and efficiency of our IoT infrastructure. Diffco has proven to be a reliable partner with exceptional expertise. I highly recommend their services.
David C ThompsonSenior Digital Initiatives director at ChemTreatThe quality and consistency of the team make Diffco stand out from other vendors.
Art DanielovCEO at FlashgridThey were communicative, consultative, and helpful. They went above and beyond all the way. What an amazing team. I will work with them again and again.
Don MarklandCEO at Accountability NowDiffco turned our concept into a polished product from scratch, delivering on a tight timeline. Clear communication, organized project management, and a strong mix of creativity and technical expertise produced an app that exceeded our vision.
Mason MeninCo-founder at WYA Group, Inc.
Between first funding and Series B
You don’t have a CTO.
You have a dozen CTO decisions waiting.
Nobody’s job is to get them right, and the wrong call can cost seven figures to undo. These are the ones we see most.
Architecture picked by a freelancer
The stack is whatever the first person knew. Nobody has checked whether it survives twelve months of growth.
An agency nobody is challenging
Vendors propose; someone has to evaluate. Without technical leadership on your side, scope, cost and quality all drift in the vendor’s favor.
Hiring engineers you can’t assess
You can’t interview for a skill you don’t have, and early engineering hires are the most expensive ones to get wrong.
Investors asking technical questions
Due diligence wants architecture diagrams, a security posture, a roadmap and a defensible team plan, from someone who can handle the follow-ups.
An AI strategy that’s just a feature list
Every board wants AI in the product. Someone has to say which use cases are real, what data they need, and what production actually requires.
When we’ll say no
A fractional CTO is the right call when the decisions are real but the workload isn’t forty hours a week yet. If you already need a full-time CTO, we’ll say so on the first call, and help you hire one.
How a fractional CTO engagement runs
Leadership first.
Building only when the plan calls for it.
Assessment: your plan, first draft
A few days to two weeks. Our agents read everything you have (codebase, docs, past decisions, call notes) and a CTO-level architect turns it into goals, the rules that must never be broken, and the questions nobody has asked yet.
You get:A written assessment, a decision log with alternatives, and a prioritized 90-day plan you can use with or without us.
Ongoing leadership
A fixed monthly allocation of CTO and architect time: roadmap ownership, architecture decisions, vendor and agency oversight, hiring, board and investor support, AI strategy.
You get:Someone accountable for every technical decision, with the reasoning written down.
Build with Diffco, if you choose to
When the plan calls for building, the same architect leads a senior Diffco team: MVP, platform work, AI features, modernization. One accountable firm, no handoff.
You get:The plan executed by the people who wrote it.
Hire your team
We write the job specs, run technical interviews, and set up the engineering practices your first hires inherit, including how they’ll use AI tooling.
You get:An in-house team that starts on your standards, not theirs.
Hand over
When you hire a full-time CTO, we transition with documentation, decision logs and a clean architecture, then step back or stay on as delivery partner.
You get:A successor who inherits a system, not a mystery.
What’s included
The four things a CTO is accountable for
Product and technical roadmap
What to build, in what order, on what architecture, tied to business milestones and the funding plan. Revisited every month against what actually shipped, not what was promised.
Architecture and vendor decisions
Stack, cloud, data model, security posture, build-vs-buy, AI models and infrastructure. Expensive-to-reverse choices are flagged before they’re made, and every decision is logged with its alternatives.
Team and delivery oversight
Hiring plan, technical interviews, engineering practices, and oversight of any agency or freelancers already in place. Someone on your side of the table.
Investor and board support
Architecture narratives, due-diligence readiness, technical risk registers, and someone on the call who can answer the hard follow-up.
Choosing the model
Fractional CTO, development agency, or both?
Solo fractional CTODevelopment agencyDiffco fractional CTO
Technical & product leadershipOne personSometimes, via a PM
CTO and senior architect
CTO and senior architectSomeone to actually buildHire or contract separatelyTheir teamSenior team, when the plan calls for it
Senior team, when the plan calls for itAccountability for the outcomeAdviceDeliveryBoth, in one firm
Both, in one firmVendor oversightIndependentConflict of interestIndependent, including of other vendors
Independent, including of other vendorsCost modelRetainerProject or T&MMonthly leadership; build quoted after assessment
Monthly leadership; build quoted after assessmentBest whenYou already have handsYou already have a plan and a leaderYou need the decisions made and the option to build
You need the decisions made and the option to build
How we build
A CTO’s job is judgment.
Code is the cheap part now.
Knowing what to build first, which foundation still holds at ten times the users, and what not to build at all. That’s where a company’s technical money is won or lost, and it’s the job a Diffco fractional CTO does.
When the plan calls for building, the same method runs the build. Senior engineers decide; more than 100 AI agents per engineer build around the clock inside a plan, with automatic checks on every change; a person watches the result work and signs off. Every decision that matters is made by a person and stays on record, which is exactly the record a CTO owes a board.
The loop, from decision to shipped
- You say what you want
- We show what it affects
- You approve
- Agents build inside the plan, with automatic checks on every change
- A person watches it work and signs off
- Daysto a first draft of your plan
- 100+ agentsAI agents per engineer when we build
- Everyarchitecture decision written down with the alternative
- Week 1the full plan is yours, with or without us
Why a fractional CTO from Diffco
Leadership that has shipped,
from a firm that still ships.
A CTO who runs production today
Eugene Nasonov co-founded Diffco in 2008 and still directs delivery on client systems, with 100+ AI agents per engineer working inside the plan. Advice comes from current practice, not memory.
18+ years of decisions to draw on
Shipping across healthcare, finance and other regulated industries since 2008: 1,450+ products spanning SaaS, fintech, mobile and industrial IoT. Most of your decisions have a precedent we’ve lived through and written down.
Hands available when you need them
The plan can be executed by the people who wrote it. Most fractional CTOs hand you a plan and a list of agencies.
Product judgment, not just technology
Vero’s CEO told us we helped shape their AI product strategy rather than just executing tickets.
Honest about the full-time hire
We tell founders when a fractional CTO is the wrong answer, and help them hire the right one.
Investor-fluent
Alchemist Accelerator mentorship and years of due-diligence prep on both sides of the table.
Strategy that led to a build
From AI product strategy to a fund-accounting ERP for school districts
Vero, an ERP for U.S. K–12 school districts, needed technical and AI product direction as much as engineering capacity. Diffco helped shape the AI product strategy, then led end-to-end development of an ERP covering AP/AR, payroll, compliance and financial integrations, with AI surfacing anomalies and automating the close.
- AP/AR · payroll · compliancein development
Two ways to engage
Start with the assessment.
Decide the rest with the plan in hand.
Assessment
A few days to two weeks. Agents read everything you have; a CTO-level architect turns it into your plan — goals, the rules that must never be broken, what the software has to do — plus a risk register, a decision log with alternatives, a prioritized 90-day plan and a hiring-or-build recommendation. Any estimate comes as a range with the open questions that make it wide.
Fixed price, agreed up front- The plan is yours in full — use it with any team, including your own
Fractional CTO retainer
A monthly allocation of CTO and architect time, covering roadmap, architecture, vendor and hiring decisions, investor support and AI strategy. Add a Diffco delivery team when the plan calls for building.
- Allocation set after the assessment, based on the decisions in flight
- Transition plan to a full-time CTO built in
Success stories of our clients
We built the AI Moderator that runs Maze’s user research interviews
We’re building Raivan, an AI-powered next-gen veterinary PMS for M3 VIA
We built VetLeo, an AI companion pet owners ask anything about their pet
We set up AI-native development across RedTrack’s ad-tracking platform
Full development + AI agentic product discovery for Happier, a top-rated meditation app
We built the AI Moderator that runs Maze’s user research interviews
We’re building Raivan, an AI-powered next-gen veterinary PMS for M3 VIA
Explore our
amazing case studies
Let’s build something
great together.
Frequently Asked Questions
A fractional CTO owns a company’s technical and product-technology decisions part-time: architecture, roadmap, build-vs-buy, vendor and agency oversight, engineering hiring, security posture, AI strategy and investor support. At Diffco the role is filled by our CTO or a senior architect, with a delivery team available when the plan calls for building.
If you have technical leadership and a clear plan, an agency. If you have neither, a fractional CTO first — and the reason to choose Diffco’s is that the same firm can build what the plan says, without a handoff. The comparison table above is the honest version.
The initial assessment is a fixed price, agreed up front. The retainer is a monthly allocation of CTO and architect time, set after the assessment based on the decisions in flight. A full-time Silicon Valley CTO costs considerably more in salary and equity — which is the point until the workload justifies it.
The allocation is set after the assessment, based on the decisions in flight, and hours flex sprint to sprint. Terms are agreed in the SOW.
No. The assessment recommends what’s right — sometimes that’s your existing team, sometimes another vendor, sometimes a full-time hire. When it is a Diffco build, it’s priced separately and you decide.
Yes: architecture narratives, security posture, technical risk register, team plan, and someone on the diligence call who can answer follow-ups. We’d rather prepare you before the round than patch during it.
Yes. We write specs, run technical interviews and set up the engineering practices — including AI tooling — your hires inherit. A good fractional engagement plans its own end.
Yes. We translate, we decide with you, and we don’t expect you to already know. You’ll read one page that shows what’s finished, what’s waiting on your decision, and what needs a second look — no new tools to learn.
You do, in full, from the first week. Goals, specifications, the decision log and acceptance standards are plain files that live beside your code — yours to keep and take anywhere, including to your future full-time CTO. That’s the point of a fractional engagement done honestly.
Need other services?
Fractional AI PartnerAI leadership and a senior engineering team in one firm, to get AI into production on the systems you already run.
Fintech Software DevelopmentPayments, banking platforms, fund accounting and receipt AI, built where money correctness comes first.
AI-Driven Product DiscoveryTwo weeks to answer “should we build this, and what would it cost to run,” before you spend six months finding out.
Custom Software DevelopmentWeb apps, platforms, and internal tools, built in weeks instead of months, from PoC to production.
Team AugmentationSenior engineers who join your team, fit your workflow and culture, and start shipping from week one.
