We are happi

We are a highly experienced team, that loves problem solving and coding. We are passionate about programming languages, Erlang in particular, and language design.

Our previous experience includes everything from building highly scalable and fault tolerant systems for the Swedish payment industry, assignments for health care projects and startups, to design and development of a cloud-based AI service to optimize material and energy consumption in laser cutting of sheet metal parts.

In short - we have the competence, experience and drive that meets the needs of both your demands and your wishes.

Erik Stenman


    “My vast experience and skills within both frontend and backend languages and architecture makes me a complete hacker.”

  • PhD in Computer Science from Uppsala University.
  • Former CTO of Klarna. Built the Engineering Department from scratch in 2005 to about 80 people in 2010.

Tobias Lindahl


    “I´m an expert backend hacker within Erlang, compilers, virtual machines, optimization and runtime systems.”

  • Master of Science in Engineering Physics from Uppsala University.
  • Former member of Klarna's Technical Advisory Board and Architect group.

Jim Wilenius


    “My specialities are foremost within java, backend, discrete optimization, and architecture.”

  • PhD in Computer Science from Uppsala University.
  • Previously headed up the R&D team at Tomologic, responsible for designing and implementing Tomologic's core optimization service.

Richard Carlsson


    “I have deep skills within compilers, virtual machines, domain specific languages, runtime systems, and development tools.”

  • Master in Computer Science from Uppsala University.
  • Member of Klarna’s core team for many years.
  • Has contributed to many parts of the Erlang standard libraries, compiler, runtime system, and the Erlang language itself.

Max Perea Düring


    “I'm a versatile developer and a pragmatic problem solver, specialized in optimization and systems programming.”

  • Master of Science in Computer and Information Engineering from Uppsala University.
  • Former member of the Optimisation research group at Uppsala University.

Mikael Lindmark


    “Coding in Erlang.”

    Mikael spent over 15 years at Klarna and was involved in most parts of Klarna's systems.

HappiHacking Delivers

Experienced team with expertise in complex problem-solving:
  • Ex Klarna CTO and Architects and developers.
  • Formal Computer Science education with Ph.D. degrees.
  • from working with clients such as WhatsApp, Deutsche Telekom, Nynja, Delta Exchange, and EMQx.
  • The team's exceptional ability to tackle non-trivial problems and provide state-of-the-art solutions sets HappiHacking apart in the market.
Full-Service Project Solutions:
  • Can bring ideas to life, from paper to working implementation.
  • HappiHacking offers end-to-end project management, covering all aspects of software development, system architecture, and project management, ensuring a seamless and successful experience for clients.
Custom-Tailored Approach:
HappiHacking takes the time to understand each client's specific requirements, goals, and challenges, allowing them to deliver solutions that are perfectly aligned with the client's vision.
Passion and Dedication:
  • The team is passionate about code.
  • The team's love for coding and problem-solving drives them to excel in their work and exceed client expectations, ensuring that the solutions provided are not just effective but also exceed expectations.
Tech Lead Mentoring:
HappiHacking's unique mentoring approach fosters collaboration, knowledge sharing, and growth within client teams, turning system validation into an opportunity for improvement.
Niche Technology Skills:
  • Focus on high-performance transactional systems.
  • HappiHacking excels in areas such as backend solutions, transaction-heavy systems, AI, machine learning, and blockchain technology, enabling them to deliver innovative solutions across various industries.
Ethical and Purpose-Driven:
HappiHacking focuses on working with ethical companies and strives to make the world a better place, ensuring that their work contributes to a positive impact on society.
Uniquely balanced team:
  • HappiHacking has Starters, Implementers, and Finishers.
  • HappiHacking has Managers (Product and Project), Designers (System and UX), Architects (Software), Leads (Tech), Developers (most languages), Testers (property-based), and DevOps (Reliability engineers).

Associates and Subcontractors

A.k.a. Friends of HappiHacking

Martin Creathorn

VP of Sales

    “Helping customers.”

    Martin has over 20 years’ international experience of business transformation, improving financial & operational performance. Successful executive in sales, operations, development, and change management.

Mikael Zayenz Lagerkvist


    “Knows everything.”

    Zayenz is an experienced software engineer with a range of skills andinterests. With a background in research, implementation, and use ofconstraint programming systems for solving combinatorial optimizationproblems Zayenz has a strong theoretical and practical foundation forsolving complex algorithmic problems. His goal is always to solve businessrelevant problems using pragmatic technology choices.

Magnus Rattfeldt



    Magnus is an experienced computer scientist with a solid 20+ year background from both academia and industry. His PhD thesis opened up new alternatives for solving combinatorial optimization problems, and during his tenure at SICS (now RISE), he was a key developer of the SICStus Prolog award-winning constraint programming engine. His focus has always been various sub fields in optimization, such as scheduling, or packing and placement. He is also a very experienced software engineer, having built and managed several complex cloud based systems.

Dincho Todorov

Reliability Engineer

    “The infrastructure IS code.”

Johannes Bahngoura

UX/UI design and Project Manager

    “Move it 2 pixels to the left…”

    Johannes is a seasoned multidisciplinary designer and project manager with extensive experience in web, desktop, and mobile design for games and apps. With his keen eye for detail and birds eye view thinking, he offers a comprehensive perspective on problem-solving and project execution.

Hans Svensson


    “Let's write a compiler for that.”

Thomas Arts


    “Have you tested that?”

    Former professor in computer science at Chalmers and CTO of Quviq.

    Well known for being able to break all software with testing techniques that automatically generate test cases from a description of the system. If Thomas cannot find an error in your software, you are going to sleep well when your software runs in production.

Anna Attefall

Project Manager

    “I´m a pragmatic project manager that believes in the power of good people and a good team.”

  • Master of Science in Computer Science from Uppsala University.
  • Team leader, project manager and CEO of startup companies.
  • Wide experience from IT, Swedish and Nordic Health care and medical technology.

Enjoy our passion with others!

We also like to discuss interesting topics together with others. If you're the same, we recommend that you join one of these groups to keep up to date with events and perhaps meet up with us.

BEAM Languages United

BEAM Languages United


We really like the BEAM.

Erlang Ecosystem Foundation

Erlang Ecosystem Foundation


We really like the erlang Ecososystem.

Func Prog STHLM

Func Prog STHLM


We really like functional programming.

Erlang Meet Up Stockholm

Erlang Meet Up Stockholm


If you missed it, we just want to state that we really like Erlang.

Let’s talk and work together!

Happi Hacking AB
Munkbrogatan 2, 5 tr
111 27 Stockholm