Microservices architecture breaks applications into small, loosely coupled services. Each service handles a specific business capability and communicates with other services via well-defined APIs.
Contrasts with monolithic architecture where an entire application is built as one unit. Microservices offer benefits but introduce complexity.
Microservices Principles
Single Responsibility: Each service has one reason to change. A user service manages user data. A payment service handles payments.
Loose Coupling: Services should not depend on each other's internal implementation. They communicate through APIs.
High Cohesion: Related functionality groups within services. Services should be cohesive units.
Independent Deployment: Services deploy independently. Updating one service should not require updating others.
Decentralised Data Management: Each service manages its own data. Services do not share databases.
Service Communication
Synchronous: Services make HTTP or gRPC requests waiting for responses. Simple but creates coupling.
Asynchronous: Services publish events other services subscribe to. Decouples services but introduces complexity.
Benefits of Microservices
Scalability: Scaling individual services is possible. If payment service receives heavy load, only that service scales.
Technology Diversity: Different services can use different technologies. A payment service might use Java; a content service might use Node.js.
Faster Deployment: Smaller teams own services. Deploys are smaller and faster.
Resilience: Failure of one service does not necessarily bring down the entire application.
Organisational Alignment: Service ownership aligns with team structures.
Challenges of Microservices
Complexity: Debugging failures across services is complex. Network reliability issues arise. Operations become more difficult.
Distributed Transactions: Ensuring consistency across services is challenging. Transactions spanning services are complex.
Data Consistency: With decentralised data management, ensuring consistency is difficult.
Network Dependency: Services depend on network reliability. Network partitions cause problems.
When to Use Microservices
Large Applications: Microservices fit applications with diverse functionality.
Multiple Teams: Organisations with many teams benefit from clear service boundaries.
Rapid Iteration: Different services can evolve independently.
Scaling Requirements: Scaling specific components becomes important.
Monolith to Microservices
Many successful applications start monolithic. As they grow, decomposing into microservices becomes valuable. Attempting to build microservices from the start is often premature.
Containerisation with Microservices
Docker containers package services with their dependencies. Kubernetes orchestrates containers across machines. Containerisation is essential for practical microservices operations.
API Gateways
API gateways sit in front of microservices, providing a unified interface. Gateways handle authentication, routing, rate limiting, and other cross-cutting concerns.
Observability
With many services, understanding system behaviour is difficult. Logging, metrics, and distributed tracing are essential for debugging.
Circuit Breakers
When services fail, circuit breakers prevent cascading failures. Services fail fast rather than queuing up requests.
Service Discovery
In dynamic environments, services need to discover other services. Service discovery systems maintain service locations.
Saga Pattern
For transactions spanning services, the saga pattern coordinates changes across services. If one service fails, sagas undo previous changes.
PixelForce's Microservices Experience
PixelForce has designed and implemented microservices architectures for complex applications. Service boundaries are carefully defined enabling independent scaling and deployment.
The Microservices Hype
Microservices have become fashionable. However, they introduce complexity most applications do not need. Organisations should start monolithic and decompose when necessary.
The Future of Microservices
Microservices will likely remain valuable for large, complex applications. Tooling continues improving. Serverless architectures may reduce microservices infrastructure complexity.