Hietanen Consultancy

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 across the UK, the US and the EU.

Describe the problem View public work
Experienced Finnish technology consultants collaborating at an ultrawide professional workstation

Current focus

FinTech · AI agents

Selected career and client-platform outcomes

25+

Years in software

800K+

Finular registered users

99.99%

Finular platform uptime

130M+

Open-source downloads

01 / Who we help

Does any of this sound familiar?

We fit best when the system is technically difficult, commercially important, or both.

  • You run a fintech or another regulated business, and a system you depend on has become hard to change.
  • You need a senior engineer or architect who ships the code, not only the recommendations.
  • Your CTO needs more senior technical capacity without another permanent executive.
  • You are moving a critical .NET platform onto modern cloud architecture.
  • You are integrating payments, banking, KYC, credit, FX or regulatory reporting.
  • You are putting AI, language models or agents into production and want someone who has run them there.
  • You are investing in or acquiring a company and need an independent technical view of it.
  • You are a founder with a new business idea; you have sparred with an AI chatbot, and now you need the real product built.

Why Hietanen

Not an agency. Not a slide-deck consultancy.

Three things that are normally bought separately, from the same people.

01

Technical leadership

Architecture, technical strategy and the decisions a board has to sign off, from someone who has carried that responsibility (FCA SMF3) in a regulated lender.

02

Senior engineering

The person advising you can build it. Most of our hours are spent in the code, and the open-source libraries we maintain have been downloaded over 130 million times.

03

Production responsibility

Nine years of running regulated platforms after launch: incidents, audits, uptime, regulators and integrations with dozens of counterparties. The advice is shaped by that.

02 / Expertise

Strategy that reaches production.

Technical advice and implementation stay together. The same senior perspective shapes decisions, architecture and delivery.

01

Technology leadership

Fractional CTO work, technical due diligence and engineering direction grounded in years of executive and board responsibility.

CTO advisoryTeam leadershipDue diligence
02

Fintech platforms

Architecture and delivery for regulated lending, FX and international payouts, payments, credit decisioning and financial integrations.

Regulated systemsFX & paymentsSecurity
03

AI & agent engineering

Practical AI systems from model integration and agent teams to machine-learning applications that belong in production.

AI agentsLLM toolingMachine learning
04

Cloud & functional .NET

High-integrity .NET platforms using C#, F#, Azure, AWS, event-driven architecture and infrastructure as code.

F# / C#Azure / AWSArchitecture

03 / How we work

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.

Which engagement fits which situation
“We need another senior engineer, now.”EngagementEmbedded engineer(s), on a day rate
“Our CTO needs senior technical support, or we have no CTO yet.”EngagementFractional CTO, on retainer
“We have a defined architecture or integration problem to solve.”EngagementFixed-scope delivery
“We are acquiring or investing in this company and need to understand its technology.”EngagementTechnical due diligence, fixed scope
“We have an old system and do not know how to modernise it.”EngagementArchitecture assessment, fixed scope, then whichever model the findings call for

Time & materials

Embedded engineer(s)

One senior engineer or a small squad of them joins your team, on-site in London, remote, or at an international client, billed by the day and scaling up or down with your roadmap. You set the direction; we bring the seniority, the delivery habits and the code that stays maintainable after we leave.

Day rateOne engineer or a squadOn-site / remote

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

What happens next

From first conversation to handover.

  1. 01

    A conversation

    Email first, then a call about the system, the problem and the constraints. Nothing to prepare on your side.

  2. 02

    Technical discovery

    Under NDA, we look at the architecture, code, infrastructure or requirements, as far as the question needs.

  3. 03

    A written recommendation

    What we would do and in what order, with a scope and an engagement model you can take to your board.

  4. 04

    Delivery

    The senior engineer or squad joins the work, on-site or remote, billed as agreed.

  5. 05

    Handover

    Your team owns the system and the knowledge. Documentation and runbooks are part of the scope, not an extra.

UK limited company (no. 16823314) based in London SW1V, working with clients internationally, with a delivery track record in the UK, the US and the EU. From SW1V, any office in Central London or the City of London is a short journey, so on-site days are easy to arrange. Direct contracts and agency framework agreements, inside or outside IR35 as the engagement requires. NDA first; rates on request.

Ask for availability See where we have done this

04 / 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.

Fuuga social previewDeep diveFuugaRetrain open-source language models on your own data, on .NETFSharp.Azure.Quantum social previewDeep diveFSharp.Azure.QuantumHigh-level quantum computing, shown through drone swarm coordination

Swipe or browse libraries and tools

ClearBank.Net social previewAuthorClearBank.NetA typed .NET client for UK/EU banking and payment integrationsCarmelNet social previewAuthorCarmelNetFinancial platform integration for the US marketCSharp.Refactor social previewAuthorCSharp.RefactorClarifies agent-generated or legacy C# into readable codeFSharp.Refactor social previewAuthorFSharp.RefactorClarifies agent-generated or legacy F# into readable, idiomatic codeProveSDK social previewAuthorProveSDKUnofficial .NET client for the Prove identity-verification APISQLProvider social previewMaintainerSQLProviderTyped data access for F# · 910K NuGet downloadsSQLProvider.Fable social previewAuthorSQLProvider.FableSQLProvider for Fable: typed data access compiled to JavaScript, Rust and other targetsNppTreeSitter social previewAuthorNppTreeSitterTree-sitter syntax highlighting plugin for Notepad++Linq.Expression.Optimizer social previewAuthorLinq.Expression.OptimizerHigh-performance .NET expression optimization · 630K NuGet downloadsOwin.Compression social previewAuthorOwin.CompressionDeflate and GZip compression middleware for OWIN and ASP.NET CoreFSharp.Data.JsonProvider.Serializer social previewAuthorFSharp.Data.JsonProvider.SerializerFast System.Text.Json serialization for FSharp.Data's JsonProviderLINQKit social previewMaintainerLINQKitExpression-tree tooling · 133M NuGet downloadsEntityFramework.BulkInsert social previewMaintainerEntityFramework.BulkInsertHigh-volume bulk inserts for Entity Framework 6Prismatic social previewAuthorPrismaticMulti-agent AI development workspace

05 / Blueprints

Start from a 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

06 / 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 & payouts

FX and international payouts platform

3 Degrees, United States

A new FX platform for international payouts on .NET 10 and AWS, integrating Wise, Airwallex, Corpay, dLocal, Mercury, Monex USA, Moneycorp, Revolut, Bitso and Cobre, delivered in 2026 by a two-engineer team; our engineer also led the client's AI-agent engineering team across several model providers.

C#.NET 10AWSPaymentsAI agents

Fintech · Lending

Regulated lending platforms in the UK and the US

Fund Ourselves Ltd (UK) and WeLendUs Inc (US) · Finular Group

Two independently regulated lenders run concurrently on one cloud-first functional platform: Fund Ourselves in the UK (FCA-authorised) and WeLendUs in the US (Texas, Missouri, Utah), each with its own payment rails, credit policies and regulatory rules. Machine-learning credit decisioning, full infrastructure as code, in-house support operation. Integrations spanned credit bureaus (TransUnion UK and US, LexisNexis), identity and fraud (Onfido, Jumio, ThreatMetrix), banking and payments (ClearBank, GoCardless, Stripe, Plaid, ACH), open banking, FCA and HMRC reporting and Salesforce.

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 MVCC#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

Page 1 of 4

Some integrations we've helped to build

Many third-party services have been wired into the platforms above and run in production across the UK, the US, the EU and Latin America, from credit bureaus and identity checks to banking rails, FX payouts, open banking and regulatory reporting.

07 / Customers

Trusted at high stakes.

Organisations we have delivered for since 2000, directly and through employers and partners: regulated lending in the UK (Fund Ourselves) and the US (WeLendUs), FX payouts in the US (3 Degrees), finance and insurance in the EU (Tapiola), and enterprise software, energy, retail and industry across the Nordics.

A client team laughing together around a laptop in a London office, Canary Wharf in the window

Banking & finance

Energy & oil

Technology

Industry & services

08 / 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

Tuomas Hietanen

Founder · Director · CTO

MSc (Tech), Artificial Intelligence

2025—now

Hietanen Consultancy

FX and payouts platform for a US fintech, as one of two engineers; AI agent team leadership

2016—2025

Finular Group · CTO & Co-founder

Built and led two independently regulated lenders, in the UK and the 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.

Cover of Guidance for .NET Systems Development by Tuomas HietanenPublicationGuidance for .NET Systems DevelopmentDevelopment, Architecture and MaintainabilityKindle & paperback · ISBN 979-8287818418View on Amazon

09 / Contact

Bring the difficult system problem.

It starts with an email. Say what you are dealing with; the reply comes from the engineer who would do the work.

Describe the problemThe system, what it does, and what is wrong or has to change. Rough notes are fine.Ask for a written assessmentA fixed-scope review of architecture, code or infrastructure, findings in writing. Scoped and priced after your email.Ask about availabilityStart dates, day rates and retainer terms; direct or through an agency framework, inside or outside IR35.
Anything elseTuomas HietanenFounder · Hietanen Consultancy Ltdhello@hietanen.co.uk
LinkedIn GitHub profile Bitbucket portfolio

Join 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.