A product identifier lets services work independently. A product list first needs someone to select the products. How composition events provide that context without a central controller knowing every service.
Catalog owns the name, Finance owns the price, and Marketing owns the rating. How does OmNomNom turn those separate contributions into one product page?
Walking OmNomNom through the questions from the previous post and landing on five boundaries that are nothing like Product, Order, Customer, and Payment.
Service boundaries are not named into existence. They are discovered by asking who actually gets to decide, what handoffs exist, and where authority quietly leaks.
Service boundaries are not about data shape or workflow. They are about authority, and most diagrams skip the part that matters.