Decompose By Subdomain

Problem Statement

Microservice architecture structures an apppcation as a set of loosely coupled microservices and each service should be developed independently in agile manner to enable continous depvery/deployment. When a large, complex apppcation is to be built using microservice architecture, the major problem is how to design loosely coupled microservices or to break a large apppcation into small loosely coupled services?

Solution

We can define a microservice corresponding to Domain-Driven Design(DDD) subdomains. DDD refers to business as a domain and a domain can have multiple subdomains. Now each subdomain refers to different areas. For Example −

Order Management − Order Management subdomain refers to Orders.

Customer Management − Customer Management subdomain refers to Customers.

Subdomains can be further classified using following criterias −

Core − Most important and key differentiator of an apppcation.

Supporting − Business related and are used to support the business activities.

Generic − Not specific to business but are used to enhance the business operations.

Example

Consider an example of an Onpne Book Store. It can have following subdomains and corresponding microservices −

Books Catalog Management

Inventory Management

Order Management

Warranty Management

Advantages

Stable Architecture − As business subdomains are stable, this architecture is highly stable.

Cross-functional Teams − Development Teams works independently, are cross-functional and are organized around functional features instead of technical features.

Loosely Coupled Services − Developed services will be loosely coupled and cohesive.

Dis-advantages

Need good understand of Business − Business subdomains needs be indentified after understanding the business. Understanding organizational structure can help as organizations are structured based on their capabipties.