Build systems you can still understand when load, money, and people pressure arrive.
HappiHacking is the technical imprint of Erik "Happi" Stenman: writing, books, tools, courses, experiments, and advisory work around BEAM systems, payments, runtime behavior, and technical judgment.
For the curious: there is a tiny machine hiding in the banner.
Latest Essays
Notes on BEAM, architecture, production systems, software work, and the strange corners that become useful later.
2026-08-10
Staff, Not Author
How I use AI for my books
From Markdown to Print
One source pipeline that produces both PDF and ebook.
2026-08-09
The Words You Do Not Have
In 1987 English made me faster and stupider in the same week. Last month a reader caught it happening to my novel.
2026-08-07
Why I Wrote a Tech Thriller
The hacking was never the unrealistic part
2026-08-06
Books and Long-Form Work
The BEAM Book
Erlang runtime internals
A practical reference for understanding scheduling, memory, processes, and the runtime behind Erlang and Elixir systems.
PhD Thesis
Concurrent language implementation
Academic work on efficient implementation of concurrent programming languages and native code compilation for Erlang.
Erlang and OTP in Action
A classic reference
A practical Erlang and OTP book from Richard Carlsson and co-authors, included here because it belongs near this work.
Ongoing Projects
- BEAM Course Material Course notes, slides, and exercises for engineers who want a better mental model of BEAM systems.
- Now A short note on active writing, courses, tools, agent-assisted engineering practice, and operating work.
- N.I.S.S.E. A tiny interpreter and REPL used to make scheduling, message passing, and process behavior visible.
- Operate in Practice Small-system operating notes around staging, Bahnhof production, deployments, security checks, and agents.
- Talks Conference talks and notes from work on runtimes, high-volume backends, and systems that need to keep running.
Selected Systems Work
The consulting work is part of the archive because it produced lessons worth keeping. These are examples of systems, constraints, and roles.
Hidden Playgrounds and Tools
Some parts of the site are more workshop bench than publication. They are here for people who like to poke at systems directly.
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N.I.S.S.E. REPL
Type
erlin the site console Open the console with the tilde key and launch a small VM for process and scheduler experiments. - Word Index A map of recurring terms A generated index of words across the essays. It is useful for accidental trails through the archive.
- Livebook Exercises Hands-on BEAM material Generated notebooks and exercises connected to the BEAM course material.
Work With Erik
I sometimes help teams building difficult systems.
The useful fit is usually a system with real constraints: money movement, high concurrency, unclear failure modes, BEAM runtime questions, technical leadership gaps, agentic development workflows, or code that has become hard to reason about.
The work starts with understanding the system as it exists, then deciding whether a review, a focused implementation effort, a workshop, an interim technical role, or short advisory support makes sense.