Systems design / Architecture
Scalability, Reliability, High Availability
Backend systems
Software Engineering
Distributed systems
Virtual machines
Blockchain technology
Visual Basic

Erik Stenman

CEO, Happi Hacking AB


Erik Stenman has a long experience in both the technical side of software development as well as from the business and management side. This makes him well-suited to architect new systems in such a way that they fulfill business needs. He is also experienced in evaluating the design of existing systems.

He has proven his ability to lead teams to deliver successful software projects within time and budget for more than two decades.

Erik is an experienced technology and business leader, especially within FinTech and communication services. He is also one of the world's most experienced Erlang developers. He has been programming Erlang since 1994; as a master's student, a doctoral student in the HiPE research group at Uppsala University, a CSO and CTO at Klarna, and now a senior developer in several customer projects. Erik started programming in 1980 and started his first company in 1989.

As one of the very first employees at Klarna Erik started in 2005 as a development manager. Following the company's enormous expansion, Erik's responsibilities grew, and he soon became CTO, a role he combined with active participation in system development. He was the driving force behind the development and design of Klarna's main business system.

The knowledgeable and competent team that Erik built at Klarna created, with a deep understanding of the business model, a distributed financial system with the highest possible accessibility and robustness requirements.

In 2014, Erik went on to start several companies, including Happi Hacking. Since then, with his in-depth knowledge and extensive experience, he has contributed greatly to several projects, for example as a senior developer and architect for an IOT system with a data pipeline capable of handling 1 billion events per day in a secure, GDPR-compliant, and efficient manner for Deutsche Telekom.

Specializes in

Today Erik specializes in the management of software projects, organizational expansion, system performance optimization, internationalization, data modeling, and back-end development.

He excels in designing and developing new systems and services with high demands on availability, robustness, scalability, and performance.

His diverse business experience makes him well-suited for Due Diligence projects and in the validation of code and system design based on business and product demands.


2014 - now Founder Happi Hacking AB

Recruiting and managing a team of highly skilled developers.

Keywords: CEO, Consultant, Founder

Below is a selection of assignments.

2021 – now Mobile game at HappiHacking

Helping the team to deliver a new mobile puzzle game. Wrote the solver for the puzzles in C.

Keywords: Architect, Project Manager, Product Manager

Tech: C, Erlang, Dart, Flutter, GitHub projects, AWS

2022 – 2022 C++ Developer for AI Startup in stealth mode

Analysing ML models in MLIR and llvm.

Keywords: ML, AI, Compiler Technology, CI build systems

Tech: Python, C++, llvm, PyTorch, TensorFlow, MLIR, CMake

2021 – 2022 Architecture and Education for Delta Exchange

Architecture review for a high transaction crypto exchange. Course in Concurrent Programming in Erlang and Elixir.

Keywords: Crypto, FinTech, Best practices, Architecture Review, Performance, Throughput, Latency, Education, Course

Tech: BEAM, Erlang, Elixir

2020 - 2022 Video chat for Deutsche Telekom

Architecture for video conference, video on demand, and co-watching system.

Keywords: Architect, Project Manager

Tech: UML, Java, MQTT (EMQX), Rabbit MQ, Docker, Kubernetes, AWS, Postgres, Git, Gitlab, WebRTC

2020 - 2020 User models for Deutsche Telekom

Architecture and data models for the user and home configuration.

Keywords: Senior developer, Architect, Project Manager

Tech: UML, Java, Kafka, RabbitMQ, Docker, Kubernetes, AWS, Postgres, Git, Gitlab

2019 - 2020 IOT & Digital Twins for Deutsche Telekom

Responsible for the development of a data pipeline capable of handling 1 billion events per day in a secure, GDPR-compliant, and efficient manner.

Keywords: Senior developer, Architect, Project Manager

Tech: Erlang, Kafka, Docker, Kubernetes, AWS, Postgress, Git, Gitlab

Happi Studios

2014-2020 Digital Boardgames

Erik had various roles and worked with web services and configuration management, web servers, API development, database design, design of pluggable engine for game rule support, and with frontend work for websites and games.

Keywords: CEO, Consultant, Founder, System and Solution Architect, Senior Developer, Games, WebApps

Tech: Erlang, JavaScript, AWS, Ansible, HTML5, Canvas

Klarna Bank

2010 - 2014 Chief Scientist

Erik worked as an Erlang magician and evangelist who spread the word about Erlang and scalable development both inside and outside Klarna. Led the efforts for scalability and stability in Klarna's system. The work included among many other responsibilities: robustness and stability, operational monitoring, real-time performance optimization

2005 - 2010 CTO

Handled all tasks related to the expansion of Klarna’s development department from 1 to 80 people. At the same time, Erik led the development and operation of Klarna's payment system with high requirements for availability and robustness 24/7. A critical part was the performance increase in the system, to meet the exponentially increasing business needs of Klarna. The work included among many other responsibilities: Hiring & Firing, Managing Managers, Strategy and working with C-level management, Automated risk assessment of credit and fraud, Data modeling and data replication.


2003 – 2004 Postdoc, EPFL

Ecole polytechnique fédérale de Lausanne (EPFL) is a university and research institute in Lausanne, Switzerland, specializing in science and technology. As a postdoc for Martin Odersky, Erik gave compiler technology courses and was also the project manager for the team that developed Scala.

1997 – 2002 PhD, Uppsala University

As a Ph.D. student, Erik developed both Jericho, the first native code compiler for Erlang, and HiPE, the first version of the second native code compiler for Erlang. He also made performance measurements, registry allocation, and garbage collection designs.

1992 – 1997 MSc Computer Science, Uppsala University


1988 – 2002 Early Work

Erik started working with computers in 1988 for companies in Haparanda like Norrfrys, Polarica, Tuab, and Paritet. In 1989 he started his first consultancy company EJDA where he also worked until he finished his Ph.D. in 2002. Working for numerous customers including Ericsson.

2002 – 2023 Other Companies and Assignments

Erik's full resume is a bit too long to list here but some of his other work includes: Developer at Virtutech, Founder of Vexilla, Profitch, and Team Mejeri, Chairman of the board in Carvutto & Barattini & Company and A.S. Ekonomi, CTO at Doorling, Building a Blockchain for æternity, Due Diligence Analyst for TidyApp, Due Diligence Analyst for Kayamo Group Ltd, Migration Assessment Finoa, Interim CTO at Laya Technologies, Technical and Business Advisor for Sika Health, and CTO for Kindio AB, a startup in stealth mode.

1997 – Publications and Awards

In addition to this, Erik has also written "The BEAM book" and articles about Erlang, presented his research at several academic conferences and workshops, and was awarded the "Erlang User of the Year" during his time in the HiPE research group. He was also the project leader for the group that developed the first version of Scala and a university lecturer, especially in compiler technology.