# Concurrency

> A conceptual representation of several tasks in progress over overlapping time, with their access to shared state coordinated.

Record: `architecture:concurrency`
Kind: model
Layer: [Performance Core](https://banes-lab.com/records/layer/performance-core.md)
Severity: contextual
Scope: runtime, service, algorithm
Canonical: https://banes-lab.com/ontology#architecture-concurrency

Listed in [Architecture principles](https://banes-lab.com/api/records/architecture.md), after [Statelessness](https://banes-lab.com/records/architecture/statelessness.md) and before [Parallelism](https://banes-lab.com/records/architecture/parallelism.md).

## Repair

- Refactored by: Add Synchronization, Use Immutable State
- Detected by: data races, flaky concurrent tests
- Violated by: unsafe shared mutation
- Measured by: [throughput](https://banes-lab.com/records/architecture/throughput.md), race count
- Enforced by: race detectors, [tests](https://banes-lab.com/records/lexicon/tests.md)

## Requires

- [Concurrency Control](https://banes-lab.com/records/architecture/concurrency-control.md)

## Reinforces

- [Throughput](https://banes-lab.com/records/architecture/throughput.md)

## Enables

- [Overlapping Work](https://banes-lab.com/records/lexicon/overlapping-work.md)

## Conflicts with

- [Race Conditions](https://banes-lab.com/records/lexicon/race-conditions.md)

## In tension with

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

## Tensions

- [Concurrency / Complexity](https://banes-lab.com/records/tension/complexity-concurrency.md)

## Severity

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

## Category

- [Scalability / Performance / Optimization](https://banes-lab.com/records/architecture-category/scalability-performance-optimization.md)

## Linked from

- [Orchestration as declared structure](https://banes-lab.com/pag/orchestration/declared-structure.md)
- [Scalability / Performance / Optimization](https://banes-lab.com/ontology/principles/architecture-category-scalability-performance-optimization.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)
- [Quality Attributes](https://banes-lab.com/ontology/lexicon/lexicon-category-quality-attributes.md)
- [Scalability / Performance / Optimization](https://banes-lab.com/ontology/lexicon/lexicon-category-scalability-performance-optimization.md)
- [Severity levels](https://banes-lab.com/ontology/schema/the-vocabulary-severity.md)
- [The resolutions](https://banes-lab.com/ontology/schema/the-resolutions.md)