Technology leadership
Fractional CTO work, technical due diligence and engineering direction grounded in years of executive and board responsibility.
CTO advisoryTeam leadershipDue diligence
Fintech · AI · Cloud · Functional .NET
Senior engineering for systems that cannot afford ambiguity.
Hietanen Consultancy brings CTO-level judgment and hands-on delivery to regulated fintech, AI and complex cloud platforms.
Current focus
FinTech · AI agents
Selected career and client-platform outcomes
25+
Years in software
9
Years as Finular CTO
800K+
Finular registered users
99.99%
Finular platform uptime
01 / Expertise
Strategy that reaches production.
Technical advice and implementation stay together. The same senior perspective shapes the decision, architecture and delivery.
Fintech platforms
Architecture and delivery for regulated lending, FX trading, payments, credit decisioning and financial integrations.
Regulated systemsFX & paymentsSecurity
AI & agent engineering
Practical AI systems from model integration and agent teams to machine-learning applications that belong in production.
AI agentsLLM toolingMachine learning
Cloud & functional .NET
High-integrity .NET platforms using C#, F#, AWS, Azure, event-driven design and infrastructure as code.
F# / C#AWS / AzureArchitecture
02 / How we work
Senior engineer(s), embedded where the work is.
Most of our work is straightforward: an experienced engineer, or several, joins your team and is billed for the time spent, on site or remote. Everything else on this page is what that engineer brings along.
Time & materials
Embedded engineer(s)
One or more senior engineers join your team, on site in London, remote, or at an international client, billed by the day. You set the direction; we bring the seniority, the delivery habits and the code that stays maintainable after we leave.
Day rateOn-site / remoteWeekly reporting
Time & materials
Team extension
A small squad delivered as a unit — lead, engineers and working practices — for capacity that is productive in week one rather than quarter two. Scales up and down with your roadmap.
Lead + engineersYour backlogFlexible size
Monthly retainer
Fractional CTO
Technology leadership for a fixed number of days a month: architecture, hiring, vendor and board conversations, technical due diligence for investors and acquirers.
RetainerBoard-levelDue diligence
Fixed price
Fixed-scope delivery
A defined outcome at an agreed price, often starting from one of the blueprints below: an integration, a migration, a proof of concept with a production path.
Agreed scopeBlueprint startHandover included
UK limited company (no. 16823314), London based, working with clients internationally. Direct contracts and agency framework agreements, inside or outside IR35 as the engagement requires. NDA first, rates on request.
03 / Public work
Open source we maintain, running in production.
Not experiments: libraries and tools that other teams ship with every day, from typed data access and expression-tree optimisation to banking integrations and developer tooling, with well over 130 million downloads between them.
Deep diveFuugaTrain, fine-tune and serve your own language models on .NETSwipe or browse libraries and tools
AuthorPrismaticMulti-agent AI development workspace04 / Blueprints
Start from a working template.
Every engagement can begin from a proven public repository: a running first implementation to build on, not a slide deck or a black box.
Swipe or browse blueprints
01
Stripe payments
Built on FunStripe.Sample
A practical starting point for typed Stripe payment flows, from checkout through integration handling.
PaymentsStripeF#
02
Mobile application
Built on fabulousMauiTutorial
A cross-platform foundation for building Android and iOS applications with .NET MAUI and F#.
AndroidiOS.NET MAUI
03
Mobile web application
Built on Kasino
A touch-first web app that installs like a native one and works offline: a complete game written in F# and compiled to run in any browser, with no app-store round trip.
04
Enterprise web application
Built on WebsitePlayground
A full-stack starting point for line-of-business web applications: typed from the database to the browser, ready to grow into a product.
WebFull stackF#
05
Event-driven architecture
Built on SimpleCQRS-FSharp
A clear, minimal reference for CQRS and event sourcing: commands, events and read models you can reason about before scaling up.
CQRSEvent sourcingArchitecture
06
Unity games
Built on Roll-a-ball-FSharp
A small, working Unity example that demonstrates functional game development with F#.
UnityGamesF#
05 / Reference projects
Solutions we have helped to build.
A selection of delivery work we have been part of, sometimes leading and often as one team among many, across fintech, insurance, enterprise software, retail analytics and energy: regulated platforms, high-volume products and the frameworks that let teams ship them faster.
Page 1 of 4
Fintech · FX
FX trading platform
3 Degrees, United States
A new FX trading platform integrating a wide set of FX venue and market-data APIs on .NET 10 and AWS, alongside leading an AI-agent engineering team working across several model providers.
C#.NET 10AWSAI agents
Fintech · Lending
FCA-regulated peer-to-peer lending platform
Fund Ourselves Ltd (UK) and WeLendUs Inc (US) · Finular Group
Built from the ground up on a cloud-first functional architecture, then converted for the US market with new payment rails, credit policies and regulatory rules. Machine-learning credit decisioning, full infrastructure as code, in-house support operation.
800K+ registered users · 99.99% uptime · $200M+ capital raised
F#AzureMachine learningFarmer IaC
Enterprise · Procurement
Purchase-to-Pay for global enterprises
Basware
Lead engineer and coding architect on the next-generation invoice-automation and order-matching product: straight-through accounts payable with 100% paperless processing and ERP integration, in a Scrum programme of over a hundred developers across Finland and India.
1M+ users · 2,000 enterprise customers
C#Reactive ExtensionsWCFEntity FrameworkSQL Server
Insurance
Online insurance store
Tapiola Group
Consolidated separate insurance product calculators into one consumer web store with a shopping cart, delivered with test-driven development and continuous integration.
ASP.NET MVCF#WCFSQL Server
Insurance · Finance
Forms application framework
Tapiola Group
Architecture and framework for over seventy internet form applications, more than a thousand pages in total, running across load-balanced web servers and a SQL cluster.
5-person team, one year · per-application cost cut to a third
C#SQL ServerContent Management Server
Retail · Analytics
Daily retail sales analytics
Analyse Solutions Finland
A service analysing daily product sales across the major Finnish store chains for retailers and manufacturers: terabyte-scale data warehouse processed through multidimensional OLAP cubes.
Analysis ServicesTeradataOLAP
Corporate treasury
Global treasury management
Worldwide industrial enterprise
Browser-based centralised treasury for a multinational: cash-flow forecasting, currency-risk management, internal FX trade and group-wide reporting, later customised for further clients.
SQL ServerVisual Basic.NET
Energy
Power-plant outage optimisation
Fortum
An intranet tool that models plant outages and computes the minimum-cost plan for resources and time on a dedicated optimisation server, reporting as text and project schedules.
SQL ServerVisual BasicRISKOptimizer
06 / Customers
Trusted where the stakes are high.
Organisations we have delivered for since 2000, directly and through employers and partners: banks and insurers, energy and oil, retail, industry and technology.
Banking & finance
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Retail
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Technology
- WM-data
- Infonet
- Flucticiel
- Exidio
- Analyse² Solutions
Industry & services
- Delta-Auto
- Trackway
- KissFM
07 / Founder
Led by Tuomas Hietanen.
Director, CTO and still a working engineer. Every engagement is led or reviewed by the founder, and the career below is the standard the rest of the team is hired against.
Tuomas Hietanen
Founder · Director · CTO
MSc (Tech), Artificial Intelligence
2025—now
Hietanen Consultancy
Fintech FX platform engineering and AI agent team leadership
2016—2025
Finular Group · CTO & Co-founder
Built and led regulated lending platforms across the UK and US
2010—2016
Basware · Lead Software Engineer
Enterprise purchase-to-pay architecture at global scale
2000—2010
Tieto-Tapiola & JA Tietoteollisuus
Finance, insurance and enterprise software engineering
Tuomas holds a Master of Science in Technology specialising in artificial intelligence, with additional business administration studies. He founded the Greater Helsinki Area F# User Group, maintains SQLProvider and LINQKit, and is a published author on .NET systems development.
PublicationGuidance for .NET Systems DevelopmentDevelopment, Architecture and MaintainabilityKindle & paperback · ISBN 979-8287818418View on Amazon08 / Contact
Bring the difficult system problem.
For technology leadership, architecture reviews or hands-on engineering in fintech, AI and cloud platforms, get in touch directly.
Contact hereTuomas HietanenFounder · Hietanen Consultancy LtdMessage on LinkedInJoin the team
We are growing. If you are a senior engineer who prefers typed, functional code and systems that have to be right, we would like to hear from you.