# Synchronous Chain Trap

> A defect in which one request depends on a deep chain of blocking synchronous remote calls, so one slow link stalls the whole request.

Record: `architecture:synchronous-chain-trap`
Kind: anti-pattern
Layer: [Enforcement Core](https://banes-lab.com/records/layer/enforcement-core.md)
Severity: discouraged
Scope: modularity
Aliases: Blocking Synchronous Chains
Canonical: https://banes-lab.com/ontology#architecture-synchronous-chain-trap

Listed in [Architecture principles](https://banes-lab.com/api/records/architecture.md), after [Cyclic Deployment Dependency](https://banes-lab.com/records/architecture/cyclic-deployment-dependency.md) and before [Chatty Interface](https://banes-lab.com/records/architecture/chatty-interface.md).

## Repair

- Refactored by: collapse_reads, introduce_async_event, cache_read_model, apply_timeout_bulkhead
- Detected by: sync_depth_above_threshold, request_path_many_remote_calls, cascading_timeout
- Violated by: Build deep request-time chains across services or modules, making latency, availability, and failure behavior multiplicative.
- Measured by: synchronous call depth per request path
- Enforced by: call-depth limits in architecture review, timeout and bulkhead policies

## Severity

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

## Category

- [Anti-patterns](https://banes-lab.com/records/architecture-category/anti-patterns.md)

## Force

- [Modularity](https://banes-lab.com/records/force/modularity.md)

## Negated by

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

## Linked from

- [Anti-patterns](https://banes-lab.com/ontology/principles/architecture-category-anti-patterns.md)
- [Event / Messaging / Asynchronous Architecture](https://banes-lab.com/ontology/principles/architecture-category-event-messaging-asynchronous-architecture.md)
- [Severity levels](https://banes-lab.com/ontology/schema/the-vocabulary-severity.md)
- [The forces](https://banes-lab.com/ontology/schema/the-forces.md)