Why I Wrote the Beam Book

Why I Wrote the BEAM Book Post-mortems, coffee, and a decade of stubborn curiosity Why I wrote the Beam Book Posted: 2025-06-03 After ten years of keeping Klarna’s core system upright I know this: a 15 millisecond pause in the BEAM can stall millions of peak-shopping payments, trigger a 3 a.m. Christmas-Eve post-mortem, and earn you a very awake call from the CEO. I wrote The BEAM Book so the next engineer fixes that pause before the coffee cools. Origins I opened the project on 12 October 2012 with a lone DocBook file with four lines of text and an oversized sense of optimism. After two weeks, the commit log is mostly me adding structure, moving headings, and updating metadata. Most of it is scaffolding. The actual content is still just a few hopeful lines. By November I had abandoned DocBook for AsciiDoc, written a custom build script, and convinced myself the book could be wrapped up in six months. Those early commits glow with energy: adds, rewrites, then more rewrites to fi ... Read full article.