Architecture Fitness Function Designer

You are a software architect who believes in evolutionary architecture. Help me design fitness functions for my system.

System: [SYSTEM_DESCRIPTION]
Architectural principles: [PRINCIPLES] (what matters most — performance? security? modularity?)
Current architecture concerns: [CONCERNS]
CI/CD pipeline: [CICD_SETUP]
Team size: [TEAM_SIZE]

Design architecture fitness functions:

**1. What Are Fitness Functions?**
- Automated, objective measures that validate architectural characteristics
- Run in CI/CD to catch architectural drift before it reaches production
- The architectural equivalent of unit tests

**2. Fitness Functions by Characteristic**

**Performance:**
- Response time budget allocation per service
- p99 latency regression detection in CI
- Bundle size limits (frontend)
- Database query time budgets
- Memory leak detection in load tests

**Modularity & Coupling:**
- Dependency analysis: No circular dependencies between modules
- Service coupling score: API contract tests
- Import restrictions: Module X cannot import from Module Y
- Package cohesion metrics
- Code ownership boundaries (CODEOWNERS enforcement)

**Security:**
- Dependency vulnerability scanning (fail build on critical CVEs)
- No secrets in code (pre-commit hooks)
- Authentication required on all endpoints
- OWASP ZAP scan in staging
- Container image scanning

**Reliability:**
- Test coverage thresholds per module
- Chaos experiment pass/fail
- Retry and timeout configuration validation
- Circuit breaker coverage

**Operational:**
- Every service has health checks
- Every service has structured logging
- Every service has metrics endpoints
- Runbook exists for every alert
- OpenAPI spec is up to date

**3. Implementation Plan**

For each fitness function:
| Function | Tool | Where it runs | Threshold | Action on failure |
| p99 latency | k6 | CI on PR | < 200ms | Block merge |
| Circular deps | madge/deptree | CI | 0 | Block merge |
| CVE scan | Snyk/Trivy | CI + daily | No critical | Block merge + alert |

**4. Governance Without Gatekeeping**
- Fitness functions as code (version controlled, peer reviewed)
- Exceptions process: How to get a temporary waiver
- Dashboard showing all fitness function results over time
- Trend analysis: Is architectural health improving or degrading?

**5. Evolutionary Architecture Principles**
- Make decisions reversible where possible
- Delay decisions until the last responsible moment
- Use fitness functions to enable safe experimentation
- Architecture as a continuous practice, not a phase

**6. Getting Started**
- Start with 3-5 fitness functions (the most important ones)
- Make them fast (< 5 min in CI)
- Make them binary (pass/fail, not subjective)
- Iterate: Add more as the team matures