Book: Hexagonal Architecture in Go Also by me: Thinking in Go (2-book series) — Complete Guide to Go Programming + Hexagonal Architecture in Go My project: Hermes IDE | GitHub — an IDE for developers who ship with Claude Code and other AI coding tools Me: xgabriel.com | GitHub You've seen this Slack thread. A team is six months into a "DDD rewrite," there's a 400-page book on someone's laptop, and the open question is still: should Inventory be inside the Order aggregate, or outside? Senior engineers argue both sides. The PR has 47 comments. Nothing ships. Here is the rule that resolves 90% of those threads: One aggregate change per database transaction. Everything else is eventually consistent. That's the rule. Vaughn Vernon defended it across a three-part paper called Effective Aggregate Design ( Part 1 , Part 2 , Part 3 ). Most DDD books bury it under 200 pages of context maps and ubiquitous language. In practice, it is the only aggregate-design rule worth memorising before you write any Go.…