# Fallback Pattern

> A design pattern that routes a failed call to an alternate provider or response declared in advance.

Record: `architecture:fallback-pattern`
Kind: pattern
Layer: [Correctness Core](https://banes-lab.com/records/layer/correctness-core.md)
Severity: contextual
Scope: service, dependency call
Canonical: https://banes-lab.com/ontology#architecture-fallback-pattern

Listed in [Architecture principles](https://banes-lab.com/api/records/architecture.md), after [Error Boundaries](https://banes-lab.com/records/architecture/error-boundaries.md) and before [Retry Pattern](https://banes-lab.com/records/architecture/retry-pattern.md).

## Repair

- Refactored by: Add Fallback Response/Provider
- Detected by: hard dependency in optional path
- Violated by: no alternate path for noncritical dependency
- Measured by: fallback coverage
- Enforced by: failure injection tests

## Requires

- [Alternate Behavior](https://banes-lab.com/records/lexicon/alternate-behavior.md)

## Reinforces

- [Graceful Degradation](https://banes-lab.com/records/architecture/graceful-degradation.md)

## Enables

- [Partial Availability](https://banes-lab.com/records/lexicon/partial-availability.md)

## Conflicts with

- [Single Behavior Path](https://banes-lab.com/records/lexicon/single-behavior-path.md)

## In tension with

- [Stale/Reduced Results](https://banes-lab.com/records/lexicon/stale-reduced-results.md)

## Tensions

- [Fallback Pattern / Stale/Reduced Results](https://banes-lab.com/records/tension/fallback-pattern-stale-reduced-results.md)

## Severity

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

## Category

- [Error Handling / Resilience](https://banes-lab.com/records/architecture-category/error-handling-resilience.md)

## Linked from

- [A tension has a mechanism](https://banes-lab.com/software-architecture/principles/a-tension-has-a-mechanism.md)
- [Error Handling / Resilience](https://banes-lab.com/ontology/principles/architecture-category-error-handling-resilience.md)
- [Error Handling / Resilience](https://banes-lab.com/ontology/lexicon/lexicon-category-error-handling-resilience.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)