Microservice Architecture and Design Patterns

Microservice architecture (MSA) aims to reduce overall IT costs, accelerate feature delivery, improve system resilience, and increase visibility across services.

Key design principles include scalability, availability, resilience, flexibility, autonomy, decentralized governance, fault isolation, auto‑configuration, and DevOps‑driven continuous delivery.

Decomposition patterns are presented:

By business function (e.g., order‑management, customer‑management)

By domain sub‑domains (core, supporting, generic)

By transaction (Two‑Phase Commit, noting its performance drawbacks)

Strangler pattern for migrating brown‑field monoliths

Bulkhead pattern for isolating resource pools

Sidecar pattern for augmenting services with auxiliary containers

Integration patterns include:

API‑gateway pattern as a single entry point, routing, aggregation, protocol translation, and security enforcement

Aggregator pattern for combining data from multiple services

Proxy pattern for exposing microservices behind a gateway

Routing pattern for request‑to‑service mapping

Chained and branch patterns for sequential or parallel service calls

Client‑UI composition pattern (e.g., SPA frameworks) to assemble UI from multiple service‑backed components

Database patterns discuss per‑service databases versus shared databases, emphasizing isolation, independent scaling, and the anti‑pattern nature of shared DBs for green‑field projects.

Consistency mechanisms covered are CQRS (separating command and query models) and event‑driven approaches, including saga patterns with choreography and orchestration options.

Observability patterns address log aggregation, metric collection (push vs pull), distributed tracing with trace IDs, and health‑check endpoints.

Reliability patterns such as circuit‑breaker and blue‑green deployment are described to handle downstream failures and enable zero‑downtime releases.

Cross‑cutting concerns include external configuration management, service‑discovery (client‑side like Eureka or server‑side like AWS ALB), and other operational best practices.