Second Brain v4.1.0 - Application Factory & Graceful Degradation

🎉 Major Release: Production-Ready Architecture

Release Date: August 3, 2025

What's New

1. Application Factory Pattern

• Clean separation between development, production, and testing environments
• Better testability and configuration management
• Proper startup/shutdown lifecycle handling

2. Tagged Router Architecture

• Organized API structure with routes grouped by functionality
• Enhanced Swagger UI with collapsible sections
• Modular design for easy feature addition/removal

3. Comprehensive Health Monitoring

• Full health checks at /api/v2/health
• Kubernetes-ready probes (/health/live and /health/ready)
• System metrics endpoint for resource monitoring

4. Graceful Degradation System

• Service continues operating even when components fail
• Automatic fallback: Semantic → Full-text → Keyword search
• Four degradation levels: FULL → NO_VECTOR → NO_PERSISTENCE → READONLY

5. SQLite Persistence with FTS5

• ACID compliance and concurrent access
• Full-text search with ranking via FTS5
• Auto-detection of best available storage backend

Key Improvements

• Test Coverage: 55 tests passing (up from 27)
• Security Score: 8.5/10 (all critical issues resolved)
• Code Reduction: 81% less complexity
• Performance: Sub-100ms response times

Migration from v4.0

No breaking changes! v4.1 is fully backward compatible.

What's Next (v4.2)

• PostgreSQL + pgvector for unified storage
• Complete async/await implementation
• Advanced filtering and search capabilities

Full Changelog: v4.0.0...v4.1.0