Real Decision
How responsibilities were split between services without creating accidental duplication.
Problem
Without clear boundaries, services either become tightly coupled or start reimplementing each other's logic, which increases coordination cost and erodes ownership.
Decision
Service boundaries were defined around distinct business capabilities and integration responsibilities, keeping contracts explicit and preventing operational concerns from leaking across domains.
Why Not
Split services around technologies instead of business capabilities.
Allow boundary drift as an acceptable side effect of growth.