# Event Sourcing

> A design pattern that stores state as the sequence of events that produced it and rebuilds current state by replaying them.

Record: `architecture:event-sourcing`
Kind: pattern
Layer: [Execution Core](https://banes-lab.com/records/layer/execution-core.md)
Severity: contextual
Scope: domain, persistence
Canonical: https://banes-lab.com/ontology#architecture-event-sourcing

Listed in [Architecture principles](https://banes-lab.com/api/records/architecture.md), after [Event Stream](https://banes-lab.com/records/architecture/event-stream.md) and before [CQRS](https://banes-lab.com/records/architecture/command-query-responsibility-segregation.md).

## Repair

- Refactored by: Persist Events, Build Projections
- Detected by: state changes lacking events
- Violated by: mutating state without event record
- Measured by: event/state consistency
- Enforced by: event append rules

## Requires

- [Append-Only Log](https://banes-lab.com/records/architecture/append-only-log.md)
- [Domain Events](https://banes-lab.com/records/architecture/domain-events.md)

## Reinforces

- [Auditability](https://banes-lab.com/records/architecture/auditability.md)
- [Temporal Modeling](https://banes-lab.com/records/lexicon/temporal-modeling.md)

## Enables

- [Replay](https://banes-lab.com/records/lexicon/replay.md)
- [Replay](https://banes-lab.com/records/lexicon/replay.md)

## Conflicts with

- [CRUD-Only State Persistence](https://banes-lab.com/records/lexicon/crud-only-state-persistence.md)

## In tension with

- [Query Complexity](https://banes-lab.com/records/lexicon/query-complexity.md)

## Tensions

- [Event Sourcing / Query Complexity](https://banes-lab.com/records/tension/event-sourcing-query-complexity.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)

## Enabled by

- [Event-Driven Architecture](https://banes-lab.com/records/architecture/event-driven-architecture.md)

## Reinforced by

- [CQRS](https://banes-lab.com/records/architecture/command-query-responsibility-segregation.md)

## Linked from

- [Coordination is software](https://banes-lab.com/disciplined-methodology/collaborate/coordination-is-software.md)
- [Every record has a kind](https://banes-lab.com/software-architecture/principles/every-record-has-a-kind.md)
- [Execution joins the halves](https://banes-lab.com/software-architecture/principles/execution-joins-the-halves.md)
- [Event / Messaging / Asynchronous Architecture](https://banes-lab.com/ontology/principles/architecture-category-event-messaging-asynchronous-architecture.md)
- [Observability / Auditability / Traceability](https://banes-lab.com/ontology/principles/architecture-category-observability-auditability-traceability.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)
- [Severity levels](https://banes-lab.com/ontology/schema/the-vocabulary-severity.md)
- [The resolutions](https://banes-lab.com/ontology/schema/the-resolutions.md)