I use AI coding agents every day. I believe they are reshaping how we build software, and I think the teams that adopt them deliberately will outperform those that don't. I am not writing this to warn you away from AI-assisted development. I am writing this because the loudest voices in the AI enthusiasm camp are also the most allergic to discussing what can go wrong. And that worries me more than
On Second Thought — Episode 06 The ORM hides the SQL. The cache hides the ORM. The service mesh hides the services. The operator hides the YAML, which already hid the kubelet, which already hid the container, which already hid the process. By Tuesday, nobody quite remembers what the original problem was. They are too busy configuring its sixth wrapper. This is the post about that wrapper. When som
Every team experiences incidents. The teams that grow stronger from them are the ones that take postmortems seriously — not as blame sessions, but as structured learning opportunities. Yet most postmortems end up as a wall of text nobody reads twice, filed away and forgotten until the same incident happens again six months later. This guide walks you through writing postmortems that genuinely chan
[05] When to Pull the Trigger on FIRE — Monte Carlo Says You're Already Free This is Part 5 of a 6-part series: Building Investment Systems with Python "You need 25x your annual expenses." That's the standard FIRE rule. For ¥9.6M annual expenses, that's ¥240M. Most people see that number and think: "I'll never get there." But the 25x rule assumes a fixed 4% withdrawal rate, zero income, zero ada
[04] The 90/10 Portfolio — Dividend Core + Growth Satellite with a Live Simulator This is Part 4 of a 6-part series: Building Investment Systems with Python In the manifesto, I described a 90/10 portfolio philosophy: 90% in dividend-growing core positions, 10% in a deep-value satellite aiming for 3-5x. Today we build both sides — the dividend snowball model for the core, and a live interactive s
[03] Designing a Personal Commitment Line — Two Loans, One Defense System This is Part 3 of a 6-part series: Building Investment Systems with Python Every major corporation maintains a revolving credit facility — a pre-arranged borrowing line they can draw from instantly during a crisis. They pay a commitment fee for the privilege of having this standby capacity, even when they don't use it. The
[02] Stress Testing Your Life — What Happens at -30%, -50%, -60%? This is Part 2 of a 6-part series: Building Investment Systems with Python After the 2008 financial crisis, regulators required banks to run stress tests — hypothetical scenarios where markets crash 30%, 40%, 60% — and prove they could survive. Your personal balance sheet faces the same risks. If you hold a securities-backed loan,