Event-Driven Architecture

Event-Driven Architecture addresses the problem of coordinating independent participants through event flow rather than direct synchronous control.

Cohesive Formulation

The practice is about flow views between observers through events. Its central Cohesive questions are:

Which observer emitted the event?
Is the event endogenous, output, exogenous, or input relative to each boundary?
What does delivery guarantee?
What state, projection model, process graph, or transition is affected by observing the event?

In the Model

Events decouple producers and consumers only when boundaries and meanings are explicit. One observer's endogenous event may become another observer's exogenous event. A receiving observer still interprets the event relative to its state, policies, authority, and boundary.

Adopting event flow also creates the capacity, failure, retention, replay, topology, evolution, and observability obligations described by asynchronous interaction design. Those obligations apply to the operational edge even when its broker reports no errors.

Failure Modes

The pattern fails when event schemas are treated as shared semantics, when broker delivery is mistaken for domain commitment, or when downstream consumers assume ordering, durability, or causality that the event flow does not guarantee.