# Event-Driven Architecture

> A convention of connecting services through published events, with each consumer reacting independently of the producer.

Record: `architecture:event-driven-architecture`
Kind: style
Layer: [Execution Core](https://banes-lab.com/records/layer/execution-core.md)
Severity: contextual
Scope: service, integration, system
Canonical: https://banes-lab.com/ontology#architecture-event-driven-architecture

Listed in [Architecture principles](https://banes-lab.com/api/records/architecture.md), after [Polymorphism](https://banes-lab.com/records/architecture/polymorphism.md) and before [Publish/Subscribe Pattern](https://banes-lab.com/records/architecture/publish-subscribe-pattern.md).

## Repair

- Refactored by: Publish Event, Add Outbox, Add Consumer Contract
- Detected by: missing correlation IDs, direct synchronous chains
- Violated by: non-idempotent consumers, undocumented event schemas
- Measured by: event contract coverage, [retry safety](https://banes-lab.com/records/lexicon/retry-safety.md)
- Enforced by: schema registry, idempotency tests

## Requires

- [Events](https://banes-lab.com/records/lexicon/events.md)
- [Message Contract](https://banes-lab.com/records/lexicon/message-contract.md)
- [Idempotency](https://banes-lab.com/records/architecture/idempotency.md)

## Reinforces

- [Low Coupling](https://banes-lab.com/records/architecture/low-coupling.md)
- [Asynchronous Communication](https://banes-lab.com/records/architecture/asynchronous-communication.md)

## Enables

- [Event Sourcing](https://banes-lab.com/records/architecture/event-sourcing.md)
- [CQRS](https://banes-lab.com/records/architecture/command-query-responsibility-segregation.md)
- [Saga](https://banes-lab.com/records/lexicon/saga.md)

## Conflicts with

- [Hidden Temporal Coupling](https://banes-lab.com/records/lexicon/hidden-temporal-coupling.md)

## In tension with

- [Debuggability](https://banes-lab.com/records/lexicon/debuggability.md)
- [Strong Consistency](https://banes-lab.com/records/lexicon/strong-consistency.md)

## Tensions

- [Event-Driven Architecture / Debuggability](https://banes-lab.com/records/tension/debuggability-event-driven-architecture.md)
- [Event-Driven Architecture / Strong Consistency](https://banes-lab.com/records/tension/event-driven-architecture-strong-consistency.md)

## Severity

- [contextual](https://banes-lab.com/records/vocabulary/severity-contextual.md)

## Category

- [Event / Messaging / Asynchronous Architecture](https://banes-lab.com/records/architecture-category/event-messaging-asynchronous-architecture.md)

## Required by

- [Choreography](https://banes-lab.com/records/architecture/choreography.md)

## Reinforced by

- [Event Bus](https://banes-lab.com/records/architecture/event-bus.md)
- [Domain Events](https://banes-lab.com/records/architecture/domain-events.md)
- [Observer Pattern](https://banes-lab.com/records/architecture/observer-pattern.md)

## Linked from

- [Execution joins the halves](https://banes-lab.com/software-architecture/principles/execution-joins-the-halves.md)
- [Domain Architecture](https://banes-lab.com/ontology/principles/architecture-category-domain-architecture.md)
- [Control / Coordination / Centralization](https://banes-lab.com/ontology/principles/architecture-category-control-coordination-centralization.md)
- [Core Modular Design](https://banes-lab.com/ontology/principles/architecture-category-core-modular-design.md)
- [Event / Messaging / Asynchronous Architecture](https://banes-lab.com/ontology/principles/architecture-category-event-messaging-asynchronous-architecture.md)
- [Behavioral Patterns](https://banes-lab.com/ontology/principles/architecture-category-behavioral-patterns.md)
- [Transactions / State / Concurrency](https://banes-lab.com/ontology/principles/architecture-category-transactions-state-concurrency.md)
- [Core Vocabulary](https://banes-lab.com/ontology/lexicon/lexicon-category-core-vocabulary.md)
- [Event Messaging Async](https://banes-lab.com/ontology/lexicon/lexicon-category-event-messaging-async.md)
- [Quality Attributes](https://banes-lab.com/ontology/lexicon/lexicon-category-quality-attributes.md)
- [Severity levels](https://banes-lab.com/ontology/schema/the-vocabulary-severity.md)
- [The resolutions](https://banes-lab.com/ontology/schema/the-resolutions.md)