James Freiwirth, Developer in London, United Kingdom
James is available for hire
Hire James

James Freiwirth

Verified Expert  in Engineering

SOLID Principles Developer

London, United Kingdom
Toptal Member Since
July 18, 2015

James has over 14 years experience building software in industry. He is a great problem-solver and can apply himself to many different domains. He can gather requirements and design, build, and test complete systems from beginning to end whilst communicating effectively with the business. He believes in using the latest tools and techniques to perfect his craft whilst never losing sight of the goal: delivering business value for the client.



Preferred Environment

Scala, Git, Xamarin, C#, F#, Visual Studio

The most amazing...

...thing I've built was an extremely high-performance trading grid using a combination of functional programming and a hardware-accelerated game engine.

Work Experience

Senior Software Consultant

2018 - 2019
Adaptive FInancial Consulting
  • Contributed to the construction of a low-latency crypto exchange.
  • Gathered requirements, architected, and developed for FIX Gateway.
  • Worked on tools for cross compilation allowing targeting of multiple platforms/languages.
Technologies: C#, TypeScript, Kotlin, Java

Senior Software Consultant

2017 - 2018
  • Worked on a high-volume API powering a global eCommerce brand.
  • Introduced software to reduce bureaucracy and allow faster deployments, saving both time and money.
Technologies: Azure, ASP.NET, F#, C#

Senior Software Consultant

2015 - 2016
  • Developed an electronic trading platform for commodities traditionally traded by email/phone.
  • Introduced functional programming techniques to rapidly build new applications with fewer defects.
  • Worked on an innovative moment-marketing tool.
  • Implemented CI/CD pipelines for rapid cloud deployment.
  • Implemented an event-sourced architecture to provide flexibility and allow full audit history.
Technologies: F#, C#, .NET

Vice President, Quantitative Strategies

2014 - 2015
Credit Suisse
  • Worked on the front-office building pricing application for financial derivatives.
  • Worked with a distributed team in London, New York, and Wroclaw, Poland.
  • Worked with stakeholders to gather business requirements and translated to production quality code.
Technologies: C#, F#

Software Consultant

2013 - 2014
Perfect Shuffle, Ltd.
  • Designed and developed a cloud-hosted, responsive SaaS application for delivering virtual gift cards to small retailers.
  • Designed and developed a high-performance trading grid control for financial services using F# and XNA.
Technologies: ZURB Foundation, XNA, Compass, Sass, HTML5, C#, F#

Software Consultant

2011 - 2013
Trayport Contigo
  • Worked in a mid-sized Agile team to develop Joule, a new commodity trading platform for the energy market.
  • Used TDD and BDD within the Agile setting to reduce regressions and involve stakeholders in writing requirements.
  • Used functional programming in a commercial environment.
Technologies: C#, F#

Software Consultant

2011 - 2011
  • Reverse-engineered a legacy application to gather requirements.
  • Designed and built a web application using ASP.NET MVC and C#.
  • Migrated existing application data to the new platform.
Technologies: C#, .NET

Software Consultant

2010 - 2011
ED&F Man
  • Built a web application to allow business owners to track and audit counterparty risk.
  • Integrated with external accounting systems.
  • Designed and built a custom blotter for importing data from Excel.
Technologies: ASP.NET MVC, MSMQ, C#

Software Engineer

2009 - 2010
Condé Nast Publications
  • Worked on the back end for high-volume and high-profile websites including Vogue, Glamour, Wired, and CN Traveller.
  • Built a custom asynchronous analytics platform.
  • Customized the CMS to integrate fast text searching using Lucene.
Technologies: jQuery, ASP.NET MVC, Apache Lucene, Umbraco, CSS, HTML, C#

Gift Card Systems

A SaaS web application to deliver a virtual gift card solution to small retailers.

Trayport Joule

A trading platform for energy markets.

Town Crier E-Mail Templating

A simple open-source email templating engine for .NET.

Perfect Shuffle Event Sourcing

An event sourcing framework for F#.
2006 - 2007

M.Sc. Degree in Computer Science

University of Newcastle-upon-Tyne - UK

2003 - 2006

B.Sc. Degree in Mathematics

University of Bath - UK


jQuery, XNA, Apache Lucene


Visual Studio, Git


.NET, Business Rules Engine, .NET Core, ASP.NET MVC, ServiceStack, Compass, ZURB Foundation, ASP.NET


Azure, Docker, Linux, Xamarin, Umbraco


C#, F#, JavaScript, SQL, CoffeeScript, HTML, Java, Kotlin, TypeScript, HTML5, Sass, Assembler x86, C++, C, Haskell, Scala, CSS


DevOps, Functional Programming, Test-driven Development (TDD), REST, Functional Reactive Programming, Object-oriented Programming (OOP), Agile Software Development, Behavior-driven Development (BDD)


Microsoft SQL Server, PostgreSQL, MySQL, NoSQL


SOLID Principles, SaaS, OWIN, MSMQ

Collaboration That Works

How to Work with Toptal

Toptal matches you directly with global industry experts from our network in hours—not weeks or months.


Share your needs

Discuss your requirements and refine your scope in a call with a Toptal domain expert.

Choose your talent

Get a short list of expertly matched talent within 24 hours to review, interview, and choose from.

Start your risk-free talent trial

Work with your chosen talent on a trial basis for up to two weeks. Pay only if you decide to hire them.

Top talent is in high demand.

Start hiring