# Stateless Processing

> A design rule that a processor derives each result only from its input and explicitly passed context.

Record: `architecture:stateless-processing`
Kind: principle
Layer: [Execution Core](https://banes-lab.com/records/layer/execution-core.md)
Severity: recommended
Scope: function, stream processor, service
Canonical: https://banes-lab.com/ontology#architecture-stateless-processing

Listed in [Architecture principles](https://banes-lab.com/api/records/architecture.md), after [Dataflow Architecture](https://banes-lab.com/records/architecture/dataflow-architecture.md) and before [Windowing](https://banes-lab.com/records/architecture/windowing.md).

## Repair

- Refactored by: Externalize State, Pass State Explicitly
- Detected by: mutable state across records/requests
- Violated by: hidden mutable state in processor
- Measured by: stateful operator count
- Enforced by: [code review](https://banes-lab.com/records/architecture/code-review.md), [tests](https://banes-lab.com/records/lexicon/tests.md)

## Requires

- [Explicit Inputs](https://banes-lab.com/records/lexicon/explicit-inputs.md)
- [No Hidden State](https://banes-lab.com/records/lexicon/no-hidden-state.md)

## Reinforces

- [Scalability](https://banes-lab.com/records/architecture/scalability.md)
- [Testability](https://banes-lab.com/records/architecture/testability.md)

## Enables

- [Parallel Processing](https://banes-lab.com/records/lexicon/parallel-processing.md)

## Conflicts with

- [Stateful Hidden Accumulation](https://banes-lab.com/records/lexicon/stateful-hidden-accumulation.md)

## In tension with

- [Stateful Business Rules](https://banes-lab.com/records/lexicon/stateful-business-rules.md)

## Tensions

- [Stateless Processing / Stateful Business Rules](https://banes-lab.com/records/tension/stateful-business-rules-stateless-processing.md)

## Severity

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

## Category

- [Streaming / Pipeline / Dataflow Processing](https://banes-lab.com/records/architecture-category/streaming-pipeline-dataflow-processing.md)

## Linked from

- [Correctness / Determinism / Verification](https://banes-lab.com/ontology/principles/architecture-category-correctness-determinism-verification.md)
- [Scalability / Performance / Optimization](https://banes-lab.com/ontology/principles/architecture-category-scalability-performance-optimization.md)
- [Core Vocabulary](https://banes-lab.com/ontology/lexicon/lexicon-category-core-vocabulary.md)
- [Streaming / Pipeline / Dataflow Processing](https://banes-lab.com/ontology/lexicon/lexicon-category-streaming-pipeline-dataflow-processing.md)
- [Severity levels](https://banes-lab.com/ontology/schema/the-vocabulary-severity.md)
- [The resolutions](https://banes-lab.com/ontology/schema/the-resolutions.md)