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The patterns

How to apply the patterns

Core patterns

Decomposition

Deployment patterns

Cross cutting concerns

Communication style

External API

Service discovery

Reliability

Data management

Security

Testing

Observability

UI patterns


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Pattern: Decompose by subdomain

Context

You are developing a large, complex application and want to use the microservice architecture.

Problem

How to decompose an application into services?

Forces

  • The architecture must be stable
  • Services must be cohesive and loosely coupled
  • Each team that owns one or more services must be autonomous

Solution

Define services corresponding to Domain-Driven Design (DDD) subdomains. DDD refers to the application’s problem space - the business - as the domain. A domain is consists of multiple subdomains. Each subdomain corresponds to a different part of the business.

Examples

The subdomains of an online store include:

  • Product catalog
  • Inventory management
  • Order management
  • Logistics

The corresponding microservice architecture would have services corresponding to each of these subdomains.

Resulting Context

This pattern has the following benefits:

  • Stable architecture since the subdomains are relatively stable
  • Development teams are cross-functional, autonomous, and organized around delivering business value rather than technical features
  • Services are cohesive and loosely coupled

Issues

There are the following issues to address:

  • How to identify the subdomains? Identifying subdomains and hence services requires an understanding of the business. Subdomains are identified by analyzing the business and it’s organizational structure and identifying the different areas of expertise.

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