# DBIS Core Banking System - Best Practices Guide This document provides comprehensive best practices for developing, deploying, and maintaining the DBIS Core Banking System. ## Table of Contents 1. [Code Organization](#code-organization) 2. [Security Best Practices](#security-best-practices) 3. [Performance Best Practices](#performance-best-practices) 4. [Testing Best Practices](#testing-best-practices) 5. [Documentation Best Practices](#documentation-best-practices) 6. [Deployment Best Practices](#deployment-best-practices) --- ## Code Organization ### Directory Structure ```mermaid graph TD subgraph "Recommended Structure" SRC[src/] CORE[core/
Business Logic] INTEGRATION[integration/
External Interfaces] INFRA[infrastructure/
Infrastructure Services] SHARED[shared/
Shared Utilities] CORE --> SERVICES[services/
Service Layer] CORE --> MODELS[models/
Domain Models] CORE --> ROUTES[routes/
API Routes] INTEGRATION --> API_GW[api-gateway/] INTEGRATION --> ISO[iso20022/] INTEGRATION --> HSM[hsm/] INFRA --> MONITORING[monitoring/] INFRA --> ENCRYPTION[encryption/] INFRA --> QUANTUM[quantum/] SHARED --> UTILS[utils/] SHARED --> TYPES[types/] SHARED --> CONFIG[config/] end ``` ### Best Practices 1. **Service Layer Pattern** - Keep business logic in service classes - Services should be stateless - Use dependency injection for testability 2. **Domain Models** - Use Prisma models for database entities - Create domain models for business logic - Separate data models from domain models 3. **Error Handling** - Use custom error classes - Provide meaningful error messages - Log errors with context 4. **Code Reusability** - Extract common functionality to shared utilities - Use TypeScript interfaces for contracts - Avoid code duplication --- ## Security Best Practices ### Authentication & Authorization ```mermaid sequenceDiagram participant Client participant API as API Gateway participant Auth as Auth Service participant HSM participant Service as Business Service Client->>API: Request with JWT API->>Auth: Validate JWT Auth->>HSM: Verify Signature HSM-->>Auth: Signature Valid Auth->>Auth: Check Permissions Auth-->>API: Authorized API->>Service: Process Request Service-->>Client: Response ``` ### Security Guidelines **Priority: Critical** 1. **HSM Integration** - Use HSM for all cryptographic operations - Never store private keys in code or environment variables - Rotate keys regularly - Use hardware-backed key storage 2. **Zero-Trust Authentication** - Verify every request - Use request signatures - Implement token expiration - Validate timestamps to prevent replay attacks 3. **Input Validation** - Validate all input data - Use Zod for schema validation - Sanitize user inputs - Reject malformed requests 4. **Secrets Management** - Use environment variables for secrets - Never commit secrets to version control - Use secret management services (AWS Secrets Manager, HashiCorp Vault) - Rotate secrets regularly 5. **CORS Configuration** - Never use wildcards in production - Specify exact allowed origins - Validate origin headers - Use credentials only when necessary ### Data Protection 1. **Encryption** - Encrypt data in transit (TLS 1.3) - Encrypt sensitive data at rest - Use strong encryption algorithms - Implement key rotation 2. **Audit Logging** - Log all security events - Store logs in tamper-proof storage - Enable log analysis - Retain logs per regulatory requirements --- ## Performance Best Practices ### Database Optimization ```mermaid graph LR subgraph "Database Optimization" INDEX[Proper Indexing] POOL[Connection Pooling] QUERY[Query Optimization] CACHE[Caching Strategy] end INDEX --> PERFORMANCE[Improved Performance] POOL --> PERFORMANCE QUERY --> PERFORMANCE CACHE --> PERFORMANCE ``` ### Performance Guidelines **Priority: High** 1. **Database Connection Management** - Use Prisma singleton pattern - Configure connection pooling - Monitor connection pool metrics - Implement connection retry logic 2. **Query Optimization** - Use database indexes - Avoid N+1 queries - Use select statements to limit fields - Implement pagination for large datasets 3. **Caching Strategy** - Cache frequently accessed data - Use Redis for distributed caching - Implement cache invalidation - Set appropriate TTL values 4. **Async Processing** - Use message queues for long-running tasks - Process notifications asynchronously - Implement background jobs - Use worker pools for CPU-intensive tasks 5. **API Response Optimization** - Minimize response payload size - Use compression (gzip) - Implement response caching - Use pagination for list endpoints ### Monitoring & Profiling 1. **Performance Metrics** - Track API response times - Monitor database query times - Measure cache hit rates - Track error rates 2. **Profiling** - Use APM tools (New Relic, Datadog) - Profile slow endpoints - Identify bottlenecks - Optimize hot paths --- ## Testing Best Practices ### Testing Pyramid ```mermaid graph TD subgraph "Testing Pyramid" E2E[E2E Tests
Few] INT[Integration Tests
Some] UNIT[Unit Tests
Many] end E2E --> INT INT --> UNIT ``` ### Testing Guidelines **Priority: High** 1. **Unit Testing** - Test individual functions and methods - Use mocks for external dependencies - Aim for high code coverage (>80%) - Test edge cases and error scenarios 2. **Integration Testing** - Test service interactions - Use test database - Test API endpoints - Validate data flow 3. **E2E Testing** - Test complete user flows - Use realistic test data - Test critical paths - Validate business requirements 4. **Test Data Management** - Use factories for test data - Clean up test data after tests - Use database transactions for isolation - Create reusable test fixtures 5. **Test Automation** - Run tests in CI/CD pipeline - Fail builds on test failures - Generate coverage reports - Run tests on every commit ### Test Organization ```mermaid graph TD TESTS[__tests__/] TESTS --> UNIT[unit/
Unit Tests] TESTS --> INT[integration/
Integration Tests] TESTS --> E2E[e2e/
E2E Tests] TESTS --> UTILS[utils/
Test Utilities] UNIT --> SERVICES[services/] UNIT --> MIDDLEWARE[middleware/] INT --> API[api/] INT --> DATABASE[database/] E2E --> FLOWS[flows/] ``` --- ## Documentation Best Practices ### Documentation Structure ```mermaid graph TD DOCS[docs/] DOCS --> ARCH[architecture/
Architecture Docs] DOCS --> FLOWS[flows/
Flow Documentation] DOCS --> API[api/
API Documentation] DOCS --> DEPLOY[deployment/
Deployment Guides] DOCS --> ADR[adr/
Architecture Decisions] ARCH --> DIAGRAMS[diagrams/
Visual Diagrams] ARCH --> VOLUMES[volume-*/
Volume Documentation] ``` ### Documentation Guidelines **Priority: Medium** 1. **Code Documentation** - Use JSDoc comments for functions - Document complex algorithms - Include usage examples - Document parameters and return values 2. **API Documentation** - Use OpenAPI/Swagger - Document all endpoints - Include request/response examples - Document error responses 3. **Architecture Documentation** - Document system design decisions - Use diagrams (Mermaid, ASCII) - Keep documentation up to date - Include recommendations 4. **Flow Documentation** - Document all business flows - Use sequence diagrams - Include error scenarios - Document prerequisites --- ## Deployment Best Practices ### Deployment Architecture ```mermaid graph TB subgraph "Production Environment" LB[Load Balancer] subgraph "Application Tier" APP1[App Instance 1] APP2[App Instance 2] APP3[App Instance N] end subgraph "Database Tier" DB_PRIMARY[Primary DB] DB_REPLICA1[Replica 1] DB_REPLICA2[Replica 2] end subgraph "Cache Tier" CACHE1[Redis 1] CACHE2[Redis 2] end LB --> APP1 LB --> APP2 LB --> APP3 APP1 --> DB_PRIMARY APP2 --> DB_PRIMARY APP3 --> DB_PRIMARY DB_PRIMARY --> DB_REPLICA1 DB_PRIMARY --> DB_REPLICA2 APP1 --> CACHE1 APP2 --> CACHE2 end ``` ### Deployment Guidelines **Priority: Critical** 1. **Infrastructure as Code** - Use Terraform or CloudFormation - Version control infrastructure - Automate provisioning - Test infrastructure changes 2. **CI/CD Pipeline** - Automate builds and tests - Use blue-green deployments - Implement rollback procedures - Monitor deployment health 3. **Environment Management** - Separate dev, staging, production - Use environment-specific configs - Never use production data in dev - Secure environment variables 4. **Database Migrations** - Version control migrations - Test migrations in staging - Backup before migrations - Plan rollback procedures 5. **Monitoring & Alerting** - Monitor application health - Set up alerts for critical issues - Track key metrics - Use dashboards for visibility 6. **Disaster Recovery** - Implement automated backups - Test restore procedures - Document recovery plans - Maintain RTO/RPO targets --- ## Code Quality Standards ### Code Review Checklist - [ ] Code follows style guide - [ ] Tests are included and passing - [ ] Documentation is updated - [ ] Security considerations addressed - [ ] Performance implications considered - [ ] Error handling is comprehensive - [ ] Logging is appropriate - [ ] No hardcoded values - [ ] Environment variables used correctly ### Linting & Formatting 1. **ESLint Configuration** - Use TypeScript ESLint rules - Enable strict mode - Fix linting errors before commit 2. **Prettier Configuration** - Consistent code formatting - Auto-format on save - Enforce in CI/CD 3. **Pre-commit Hooks** - Run linting - Run tests - Check formatting - Validate commits --- ## Summary Following these best practices ensures: - **Security**: Robust protection against threats - **Performance**: Optimal system performance - **Maintainability**: Easy to understand and modify - **Reliability**: Consistent and predictable behavior - **Scalability**: Ability to handle growth For specific implementation details, refer to: - [Development Guide](./development.md) - [Deployment Guide](./deployment.md) - [API Guide](./api-guide.md) - [Recommendations](./RECOMMENDATIONS.md)