Microservices Architecture

Microservices architecture is an approach to software development where a large application is decomposed into a collection of small, independently deployable services, each responsible for a specific business capability. Rather than a single monolithic application that is deployed as one unit, microservices allows teams to develop, test, scale, and deploy individual services independently. .NET Core was designed with microservices in mind from the beginning — its lightweight runtime, fast startup time, small Docker image footprint, and built-in support for health checks, distributed tracing, and container orchestration make it one of the premier platforms for building microservice architectures. Docker is the containerization technology that makes microservices practical. A Docker container packages an application and all its dependencies into a single, portable unit that runs identically on a developer's laptop, a CI/CD server, and a production Kubernetes cluster. A .NET Core application is containerized using a Dockerfile — a text file that describes the steps to build the container image. Microsoft provides official .NET SDK and Runtime base images on Docker Hub, optimized for size and security. Multi-stage builds in Dockerfiles separate the build environment (which includes the full SDK) from the runtime environment (which needs only the smaller runtime), producing lean production images. The official .NET 8 runtime Alpine image is under 50MB. Kubernetes (K8s) is the industry-standard container orchestration platform, automating deployment, scaling, self-healing, and lifecycle management of containerized applications. A .NET Core application deployed to Kubernetes is defined in YAML manifests: a Deployment specifies the container image, replica count, resource limits, environment variables, and health check probes; a Service exposes the deployment's pods as a stable network endpoint; an Ingress routes external HTTP traffic to the correct service. Kubernetes automatically rolls out new versions using rolling updates (replacing old pods one at a time to maintain availability), rolls back failed deployments, distributes pods across nodes for fault tolerance, and scales pod counts up or down based on CPU or custom metrics via the Horizontal Pod Autoscaler. Service mesh technologies like Istio and Linkerd operate at the infrastructure layer to provide cross-cutting concerns across all microservices without requiring changes to application code: mutual TLS encryption between services, intelligent traffic routing with canary deployments, circuit breaking to prevent cascading failures, distributed tracing that paints a complete call graph across dozens of services for a single user request, and centralized metric collection. gRPC — Google's high-performance binary RPC framework — is the preferred communication protocol for synchronous inter-service calls in .NET microservices, offering strongly-typed contracts via Protocol Buffers, bidirectional streaming, and significantly lower overhead than REST/JSON.

Microservices are an architectural approach where applications are built as a collection of loosely coupled, independently deployable services.