Erik Stenman
Founder of HappiHacking. Author of The BEAM Book. Builder of systems that last.
About Erik
Erik Stenman (Happi) is a senior technology leader and systems architect with three decades of experience building distributed, fault-tolerant systems. He founded HappiHacking in 2014 and continues to work with organizations that need infrastructure designed for reliability, compliance, and scale.
He holds a Ph.D. in Computer Science from Uppsala University, where his research focused on native code compilation for the Erlang virtual machine (the HiPE project). After a postdoc at EPFL in Lausanne, working with Martin Odersky on early Scala development, he joined Klarna as its first CTO.
Career Highlights
- Klarna (2005 to 2014)
- As Klarna's first CTO, Erik built the engineering department from scratch, growing it from a handful of people to roughly 80 engineers by 2010. He architected and operated Klarna's core payment infrastructure, establishing the distributed systems principles that supported the company's growth into one of Europe's leading fintech platforms.
- HappiHacking (2014 to present)
- Through HappiHacking, Erik leads consulting projects on large-scale system architecture, observability, and modernization. Clients include Deutsche Telekom (event pipelines handling over one billion daily transactions), Redcare Pharmacy (platform architecture coaching), and Scania/TRATON (vehicle-to-cloud connectivity).
- Aeternity Foundation (2017 to 2019)
- Erik designed and implemented FATE, a safer and more efficient virtual machine for smart contracts, as part of a BEAM-based blockchain optimized for verifiable, high-throughput transactions.
- Research and Academia
- Erik's doctoral work at Uppsala University produced the HiPE native code compiler for Erlang. His postdoc at EPFL contributed to compiler technology and the early development of the Scala programming language.
- Current Work
- Erik currently advises the CTO at Kivra, mentors early-stage founders at Ignite Next, and coaches architects at Redcare Pharmacy on scalable platform design.
Publications
The BEAM Book
A comprehensive guide to understanding the Erlang Runtime System (ERTS), the virtual machine that powers Erlang, Elixir, and other BEAM languages. The book covers process management, memory architecture, scheduling, garbage collection, and fault tolerance at the implementation level.
The BEAM Book reached #1 New Release on Amazon in both the US and Sweden, was featured as #1 on Hacker News, and has over 3800 stars on GitHub. Jose Valim, the creator of Elixir, is among its sponsors.
HappiHacking Systems Series
Erik is working on several additional books through HappiHacking's publishing imprint. Upcoming titles include Scalable Fintech Systems (expected 2026), Erlang by Doing (manuscript complete), and Architecture and Organization (early draft). These books address runtime behavior, language practice, organizational structure, and building under regulatory constraints.
Browse all resourcesSpeaking
Erik speaks regularly at conferences including Code BEAM, the Erlang Workshop, and fintech architecture events. His talks typically cover BEAM internals, scalable system design, and the practical challenges of building compliant financial infrastructure.
Recent topics include "Fast and Compliant: The Fintech Paradox Solved with BEAM" and a long-form interview on the BEAM Radio podcast about the history and future of the Erlang runtime.
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