REL11-BP05: Use static stability to prevent bimodal behavior
Static stability ensures your system behaves consistently regardless of the state of its dependencies. Avoid architectures that behave differently during normal operations versus failure scenarios. Design systems that can continue operating with cached data, default configurations, or degraded functionality when dependencies are unavailable.
Implementation Steps
1. Identify Dependencies
Map all external dependencies and their impact on system behavior.
2. Design Fallback Mechanisms
Implement fallback strategies that maintain consistent behavior during dependency failures.
3. Cache Critical Data
Store essential data locally to avoid dependency on external services.
4. Use Default Configurations
Define safe default values that allow continued operation.
5. Implement Graceful Degradation
Design systems to reduce functionality rather than fail completely.
Detailed Implementation
AWS Services
Primary Services
- Amazon ElastiCache: Distributed caching for consistent data access
- Amazon DynamoDB: NoSQL database with consistent performance
- AWS Lambda: Stateless compute with built-in fault tolerance
- Amazon S3: Highly available object storage for static content
Supporting Services
- Amazon CloudWatch: Monitoring without dependency on external services
- AWS Systems Manager Parameter Store: Configuration management with caching
- Amazon SQS: Asynchronous messaging with built-in redundancy
- AWS App Config: Feature flag management with local caching
Benefits
- Consistent Behavior: System operates predictably regardless of dependency state
- Reduced Cascading Failures: Prevents dependency failures from causing system-wide outages
- Improved User Experience: Graceful degradation maintains core functionality
- Operational Simplicity: Eliminates bimodal behavior that complicates troubleshooting
- Higher Availability: System remains operational even when dependencies fail