microservices-patterns

Microservices Patterns

The craft of decomposing systems into independent services and making them work reliably together. Covers decomposition strategies, communication patterns, data ownership, and the resilience patterns that keep a distributed system from cascading into total failure.

When to Use

Use for:

• Deciding whether to decompose a monolith and where to start
• Designing service boundaries using bounded contexts and domain-driven design
• Choosing between synchronous (REST/gRPC) and asynchronous (events) communication
• Implementing saga pattern for distributed transactions
• Designing API gateways and backend-for-frontend (BFF) layers
• Applying circuit breaker, bulkhead, and retry patterns
• Event sourcing and CQRS design
• Service discovery and load balancing strategies

NOT for:

• Monolith internal architecture (use database-design-patterns, api-architect)
• Serverless function design and deployment
• Kubernetes infrastructure and deployment configuration (use terraform-iac-expert)
• Service mesh configuration (Istio, Linkerd) — mention it, not the core focus
• Single-service performance optimization (use performance-profiling)

Core Decision: Monolith vs Microservices vs Modular Monolith

flowchart TD
    Start[New project or architecture review] --> TeamSize{Team size?}
    TeamSize -->|1-8 engineers| Small[Modular monolith first]
    TeamSize -->|9-25| Medium{Domain complexity?}
    TeamSize -->|25+| Large{Independent deploy needed?}

    Small --> S1[Build well-factored modules with clear boundaries]
    S1 --> S2{Growing pains?}
    S2 -->|No| S1
    S2 -->|Yes: deploy conflicts, team coupling| Extract[Extract services at natural seams]

    Medium -->|Simple, few domains| Modular[Modular monolith]
    Medium -->|Complex, many bounded contexts| MicroQ{Org structure?}
    MicroQ -->|Teams align to domains| Micro[Microservices]
    MicroQ -->|Teams are cross-functional| Modular

    Large -->|Yes, teams blocked waiting for each other| Micro
    Large -->|No, deploys are coordinated| Modular

    Micro --> Check{Check: do services deploy independently?}
    Check -->|No, they must release together| Problem[You have a distributed monolith]
    Check -->|Yes| Proceed[Proceed with microservices]