System Integration Coupling Levels

Different levels of coupling in system integration, ordered from least to most coupled:

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1. Documented Contracts

Interaction via documented protocols, data formats, and SLAs. No shared code or runtime.
Pros: Maximum autonomy, minimal dependency risk.
Cons: High alignment effort; integration issues detected late.

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2. Shared Test Suite (TCK-like)

Compliance validated through a common test suite based on shared specifications.
Pros: Behavioral consistency without runtime coupling.
Cons: Requires strict discipline; gaps emerge if tests lag behind evolving specs.

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3. Shared Library

Common logic packaged as a library consumed by multiple systems.
Pros: Reduces duplication, enforces uniform logic.
Cons: Versioning complexity; tight dependency on library evolution. Clear ownership required.

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4. Shared Framework

Systems built on a common framework dictating architecture and lifecycle.
Pros: Strong consistency, accelerates development.
Cons: High lock-in; framework changes ripple across all consumers. Governance critical.

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5. Centralized Runtime Component (API-based)

Standalone component exposes APIs; others integrate via network calls.
Pros: Clear boundaries, runtime flexibility, easier scaling.
Cons: Adds latency, operational complexity, dependency on component availability.

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6. Platform Integration

Multiple systems integrated into a single platform/runtime.
Pros: Seamless interaction, shared state, optimal performance.
Cons: High complexity; owning team manages deployment and scaling for entire platform.

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Key Considerations

Coupling level selection depends on team structure, release cadence, performance needs, and risk tolerance.
Lower coupling → autonomy, higher coordination cost.
Higher coupling → consistency, increased dependency risk.