Building event-driven systems changed how I think about software.

Services shouldn't call each other constantly. They should react to events.

Example:

User signs up → Auth emits an event

→ Notification service sends the welcome email

→ Analytics service records the signup

→ User service continues onboarding

One action. Multiple reactions.

The biggest shift is mental: you stop designing request chains and start designing system reactions. The signup service doesn't need to know who cares that a user signed up — it publishes the fact, and the system reacts.

The honest cost: debugging gets harder. A request chain fails in one place, with a stack trace.…