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 ship a clean DDD layout. Aggregates, value objects, repositories, the lot. Then a Postgres consultant looks at your orders table and asks why the primary key index is twice the size it should be and why writes started getting slower around the time the table crossed 50 million rows. The answer is sitting in your domain layer. Your OrderID is a UUID v4. Random 128 bits. Every insert lands on a different B-tree leaf page, splits it, and burns write IOPS for nothing. Aggregate identity feels like a footnote when you're sketching the domain. It is not. The ID type is the one piece of the aggregate that touches every layer: constructor, repository, index. URLs and logs too.…