Non-functional Requirements (NFRs)
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Non-functional requirements (NFRs) define the qualities and characteristics of a system, focusing on how well it performs rather than what it does. They include constraints and attributes like performance, security, usability, reliability, and scalability.
Performance
- Response Time: The system should respond to user requests within 2 seconds.
- Throughput: The system should process 100 transactions per second.
- Load Capacity: Handle 10,000 concurrent users without performance degradation.
Security
- Data Encryption: All sensitive data must be encrypted in transit and at rest.
- Authentication: Use multi-factor authentication for user access.
- Authorization: Restrict resource access based on user roles.
- Compliance: Must comply with relevant security standards (e.g., PCI DSS).
Usability
- Intuitive Navigation: Provide a user-friendly interface with clear navigation.
- Accessibility: Support users with disabilities and follow WCAG guidelines.
- User Experience (UX): Ensure a positive and engaging user experience.
Reliability
- Availability: Target 99.999% uptime.
- Mean Time Between Failures (MTBF): Minimum of 1000 hours.
- Fault Tolerance: Recover from errors and continue operating.
Scalability
- Horizontal Scalability: Add more servers to handle load.
- Vertical Scalability: Upgrade server resources.
Maintainability
- Modularity: Use modular architecture for easy updates.
- Testability: Ensure clear interfaces and components.
- Documentation: Provide comprehensive documentation.
Other NFRs
- Portability: Run on different platforms (e.g., Windows, Linux, macOS).
- Compatibility: Work with other systems and technologies.
- Cost: Stay within budget for development and maintenance.
- Storage: Have sufficient capacity for expected data volume.
- Localization: Support multiple languages and regions.
Defining and meeting these NFRs ensures your software functions properly while fulfilling broader user and business expectations.
