Monolith to Microservices

Migration Fundamentals

• Incremental migration: Implement migrations incrementally rather than using big bang approaches
• Pattern application: Apply proven decomposition patterns like the Strangler Fig Pattern to safely migrate functionality
• Technology adoption: Adopt new technologies gradually, validating their fit before committing fully
• Microservice definition: Define microservices as independently deployable services organized around business capabilities
• Value validation: Validate the business value of migration before committing significant resources
• Risk management: Manage risk by breaking migrations into small, reversible steps
• Change sequencing: Sequence changes to deliver value early and minimize disruption
• Data concerns: Address data concerns early, as they are often the most challenging aspect of migration
• Organizational readiness: Ensure organizational readiness for distributed systems before migration
• End-state vision: Maintain a clear vision of the desired end state to guide incremental changes

Planning a Migration

• Business goal alignment: Align migration plans with specific business goals and outcomes
• Migration strategy selection: Select migration strategies based on your specific context and constraints
• Team topology consideration: Consider team topology when planning service boundaries
• Migration prioritization: Prioritize migration efforts based on value, risk, and learning opportunities
• Milestone definition: Define clear milestones to track progress and demonstrate value
• Resource allocation: Allocate resources appropriately between migration and new feature development
• Stakeholder management: Manage stakeholder expectations throughout the migration process
• Incremental funding: Secure funding incrementally by demonstrating value at each stage
• Learning incorporation: Incorporate learnings from early migrations into later stages
• Exit strategy definition: Define exit strategies for when circumstances change or assumptions prove incorrect

Splitting the Monolith

• Seam identification: Identify seams in the monolith where functionality can be cleanly extracted
• Shared functionality extraction: Extract shared functionality first to establish common services
• Module extraction sequencing: Extract modules in a sequence that minimizes risk and disruption
• Interface creation: Create clean interfaces before extraction to minimize coupling
• Database decomposition: Decompose databases carefully, often as a separate step from code extraction
• Foreign key constraint management: Manage foreign key constraints during database decomposition
• Deployment coordination: Coordinate deployments carefully during transition periods
• Legacy code isolation: Isolate legacy code to prevent it from contaminating new services
• Technical debt management: Address critical technical debt before extraction when necessary
• Test coverage improvement: Improve test coverage before extraction to ensure behavior preservation

Decomposition Patterns

• Strangler Fig Pattern application: Apply the Strangler Fig Pattern to gradually migrate functionality
• Branch by Abstraction usage: Use Branch by Abstraction to manage large-scale changes
• Parallel Run implementation: Implement Parallel Runs to validate new implementations against old
• Feature Toggle utilization: Utilize Feature Toggles to control exposure of new functionality
• Decorating Collaborator application: Apply the Decorating Collaborator pattern to intercept and modify interactions
• Change Data Capture implementation: Implement Change Data Capture for database migrations
• Database View usage: Use Database Views to present restructured data while maintaining compatibility
• Database Wrapping Service creation: Create Database Wrapping Services to encapsulate database access
• Aggregate Exposing implementation: Implement Aggregate Exposing to reveal domain boundaries
• UI Composition application: Apply UI Composition to create user interfaces from multiple services

Data Decomposition Patterns

• Database-per-Service implementation: Implement Database-per-Service to ensure data autonomy
• Shared Database management: Manage Shared Database configurations during transition periods
• Schema Separation execution: Execute Schema Separation to create service-specific schemas
• Data Access Layer creation: Create service-specific Data Access Layers to isolate database changes
• Event-based communication adoption: Adopt event-based communication to reduce direct data coupling
• CQRS implementation: Implement Command Query Responsibility Segregation where appropriate
• Materialized View maintenance: Maintain Materialized Views for cross-service data requirements
• Saga Pattern usage: Use the Saga Pattern to manage distributed transactions
• Data synchronization mechanism: Establish data synchronization mechanisms during migration periods
• Master Data Management consideration: Consider Master Data Management for shared reference data

Growing Pains

• Monitoring implementation: Implement comprehensive monitoring before extracting services
• Distributed tracing adoption: Adopt distributed tracing to understand request flows
• Error handling strategy: Develop strategies for handling errors in distributed systems
• Resilience pattern application: Apply resilience patterns like Circuit Breakers and Bulkheads
• Service discovery implementation: Implement service discovery mechanisms
• Configuration management strategy: Develop strategies for managing configuration across services
• Security model adaptation: Adapt security models for distributed environments
• Network latency consideration: Consider network latency in service interactions
• Versioning strategy development: Develop strategies for API versioning and compatibility
• Deployment pipeline creation: Create deployment pipelines that support independent service deployment

Organizational Challenges

• Team structure alignment: Align team structure with service boundaries
• Ownership clarification: Clarify ownership and responsibilities for services
• Skill development planning: Plan for developing skills needed for microservice environments
• Communication pattern establishment: Establish communication patterns between teams
• Governance model implementation: Implement appropriate governance models for microservices
• Standardization balance: Balance standardization with team autonomy
• Inner source promotion: Promote inner source practices for shared components
• DevOps culture cultivation: Cultivate DevOps culture to support service ownership
• Knowledge sharing mechanism: Establish mechanisms for knowledge sharing across teams
• Organizational learning facilitation: Facilitate organizational learning during migration

Migration Strategies

• New functionality implementation: Implement new functionality as microservices first
• Extraction approach selection: Select between UI-first, Domain-first, or Infrastructure-first extraction approaches
• Bubble Context creation: Create Bubble Contexts to safely implement new models alongside old
• Evolutionary Architecture support: Support Evolutionary Architecture through appropriate technical practices
• Technical debt prioritization: Prioritize technical debt remediation that enables migration
• Legacy replacement planning: Plan legacy system replacement in manageable increments
• Integration testing strategy: Develop testing strategies appropriate for distributed systems
• Contract testing implementation: Implement contract testing between services
• Deployment coordination planning: Plan deployment coordination during transition periods
• Rollback capability maintenance: Maintain rollback capabilities throughout the migration

When Not to Use Microservices

• Complexity assessment: Assess whether the complexity of microservices is justified for your context
• Organizational readiness evaluation: Evaluate organizational readiness for microservice challenges
• Alternative consideration: Consider alternatives like modular monoliths for similar benefits with less complexity
• Cost-benefit analysis: Analyze costs and benefits specifically for your situation, not general principles
• Operational capability assessment: Assess whether you have the operational capabilities to run microservices
• Team size consideration: Consider whether your team size justifies the overhead of microservices
• System criticality evaluation: Evaluate the criticality of the system when deciding on architecture
• Domain stability assessment: Assess domain stability before committing to service boundaries
• Migration justification: Justify migration based on specific problems you’re trying to solve
• Technical maturity evaluation: Evaluate technical maturity of the organization before migrating

Key Takeaways

1. Incremental approach: Migrate to microservices incrementally, delivering value at each step
2. Pattern application: Apply proven decomposition patterns to safely extract functionality
3. Data challenge prioritization: Prioritize solving data challenges, as they’re often the most difficult aspect
4. Team alignment: Align team structures with service boundaries to optimize ownership
5. Monitoring importance: Implement comprehensive monitoring before extracting services
6. Business value focus: Focus on business value rather than technical purity when planning migrations
7. Organizational readiness: Ensure organizational readiness for the challenges of distributed systems
8. Distributed data management: Develop strategies for managing data in a distributed environment
9. Independent deployability: Design for independent deployability to realize microservice benefits
10. Migration justification: Only migrate when the benefits clearly outweigh the significant costs and complexity