The Systems Series is written and published by Erik Stenman through HappiHacking.
HappiHacking Systems Series
The HappiHacking Systems Series explores scalable architecture, runtime behavior, and ownership in high-complexity environments.
These books are written for experienced developers, architects, and technical leaders building systems that must survive scale, regulation, and failure.
Upcoming
Scalable Fintech Systems
Designing and operating fintech systems under regulatory constraints.
Status: In development · Expected 2026
Upcoming
Erlang by Doing
A practical introduction to Erlang through building real systems.
Status: Manuscript complete · Editing phase
Upcoming
Architecture & Organization
How system architecture and team structure shape each other.
Status: Early draft
About the Series
The series is published by HappiHacking, an independent technical imprint focused on scalable systems and ownership-driven architecture.
Each book addresses a different layer of system design: runtime behavior, language practice, organizational structure, and regulated environments.
A curated library of books, frameworks, and guides from the people at HappiHacking.
All Resources
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Get expert guidance on BEAM architecture, scaling challenges, or fintech compliance. 30-minute strategic session with our team.
Deep Dive: The BEAM for Developers
A hands-on course for mastering the BEAM, tracing, debugging, and scaling real systems
I found the philosophical part useful for the team to design our applications. - Shraman, Delta Exchange
Hands-on
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Certification
PhD Thesis "Efficient Implementation of Concurrent Programming Languages"
Academic deep dive into the BEAM virtual machine, Erlang runtime system (ERTS), and robust distributed systems
The days are all empty and the nights are Unreal - cookie quote from the thesis.
Academic
Research
Mastering Developer Productivity
Empowers developers to find motivation, optimize workflows, and achieve balance for professional growth
A practical, actionable course for devs and leads: Build habits, optimize workflows, and get more done—without burning out. Based on proven productivity science and developer reality.
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6 Modules
Strategic Foundations for Entrepreneurial Success
Comprehensive coaching program for building profitable, sustainable businesses from strategy to execution
Finally got my business finances under control and found my true profit drivers. - Course Graduate
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Coaching
Profit First
Kappa
A tool for keeping large Erlang codebases-developed by multiple teams-in a manageable state
Kappa was conceptualized and started by Erik Stenman at Klarna to keep massive, multi-team Erlang codebases manageable and transparent. Now open source—ideal for analytics and codebase health at scale.
Open-source
Klarna
The HappiHacking Blog
In-depth guides, real-world post-mortems, productivity tactics, and BEAM insights from the field
Thank you for writing this book! I really wanted this a few years ago as I was debugging production Elixir. - bicx, Hacker News
Weekly
Practical
Erlang and OTP in Action
A practical, experience-rich guide to Erlang and OTP by Richard Carlsson and co-authors.
A long-awaited book that covers distributed programming from so up to nuts. OTP has grown over the years. This book shows the lessons learned. - Ulf Wiger
Classic
Erlang/OTP Contributions
Contributed to Erlang/OTP during both the HiPE research era and ten years scaling Klarna.
Contributed to Erlang/OTP during the HiPE research era and throughout a decade scaling Klarna—patches, ideas, and insights that helped shape the runtime still used in production today.
Erlang
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