microservice architecture   architecting   dark energy and dark matter   loose coupling  

Dark matter force: minimize design-time coupling

a dark energy, dark matter force

When designing software it’s important to minimize design-time coupling between software elements, regardless of whether classes, packages, subdomains or services. The degree of design-time coupling between a pair of software elements is the likelihood that they need to change together for the same reason. Design-time coupling between services in a microservice architecture is especially problematic. Let’s look at why it’s a problem, how we can minimize it and why it’s an attractive force between subdomains.

Why is design-time coupling between services a problem?

If two services are loosely coupled, then a change to one service rarely requires a change to the other service. However, if two services are tightly coupled, then a change to one service often requires a change to the other service. These types of lock step changes are expensive since it typically involves breaking API changes.

For example, let’s imagine that the Order Service and Customer Service are tightly coupled. Each time a breaking changes needs to be made to the Customer Service the sequence of steps is as follows:

  1. Change the Customer Service to add a new major version of its API. The service must implement both the old and new version of its APIs until all clients have been migrated over.
  2. Migrate the Order Service to the new API version
  3. Remove the old API version from the Customer Service

What’s even worse, is that quite often the services are owned by different teams, which requires those teams to coordinate the changes. In other words, design-time coupling between services undermines team autonomy.

How to minimize design-time coupling between services

There are a couple of different ways to minimize design-time coupling between services.

Design subdomains to be loosely coupled

The first is to design subdomains to be loosely coupled. Loosely coupled subdomains can be packaged as different services. Loose design-time coupling is usually achieved by each subdomain having a stable API that encapsulates its implementation.

In general, to reduce design-time coupling, software elements, such as subdomains and services, should expose the minimum amount of information to their clients. For example, I like to use the Iceberg metaphor to describe a software element. Similarly, John Ousterhout in his book A Philosophy of Software Design describes how modules should be deep rather than shallow.

Package tightly coupled subdomains together

The second way to minimize design-time coupling between services is to package subdomains that are tightly coupled in the same service. If two subdomains are tightly coupled, then packaging them together in the same service will avoid design-time coupling between services. As a result, design-time coupling acts as an attractive force between subdomains.

microservice architecture   architecting   dark energy and dark matter   loose coupling  

Copyright © 2023 Chris Richardson • All rights reserved • Supported by Kong.

About Microservices.io

Microservices.io is brought to you by Chris Richardson. Experienced software architect, author of POJOs in Action, the creator of the original CloudFoundry.com, and the author of Microservices patterns.

Chris helps organizations improve agility and competitiveness through better software architecture. Learn more about his consulting engagements, and training workshops.


Premium content and office hours is now available for paid subscribers at premium.microservices.io.


Chris teaches comprehensive workshops for architects and developers that will enable your organization use microservices effectively.

Avoid the pitfalls of adopting microservices and learn essential topics, such as service decomposition and design and how to refactor a monolith to microservices.

Learn more

LEARN about microservices

Chris offers numerous other resources for learning the microservice architecture.

Get the book: Microservices Patterns

Read Chris Richardson's book:

Example microservices applications

Want to see an example? Check out Chris Richardson's example applications. See code

Remote consulting session

Got a specific microservice architecture-related question? For example:

  • Wondering whether your organization should adopt microservices?
  • Want to know how to migrate your monolith to microservices?
  • Facing a tricky microservice architecture design problem?

Consider signing up for a two hour, highly focussed, consulting session.

Virtual bootcamp: Distributed data patterns in a microservice architecture

My virtual bootcamp, distributed data patterns in a microservice architecture, is now open for enrollment!

It covers the key distributed data management patterns including Saga, API Composition, and CQRS.

It consists of video lectures, code labs, and a weekly ask-me-anything video conference repeated in multiple timezones.

The regular price is $395/person but use coupon KQAWEXBH to sign up for $120 (valid until November 21st, 2023). There are deeper discounts for buying multiple seats.

Learn more

Learn how to create a service template and microservice chassis

Take a look at my Manning LiveProject that teaches you how to develop a service template and microservice chassis.

Signup for the newsletter

BUILD microservices

Ready to start using the microservice architecture?

Consulting services

Engage Chris to create a microservices adoption roadmap and help you define your microservice architecture,

The Eventuate platform

Use the Eventuate.io platform to tackle distributed data management challenges in your microservices architecture.

Eventuate is Chris's latest startup. It makes it easy to use the Saga pattern to manage transactions and the CQRS pattern to implement queries.

ASSESS your architecture

Assess your application's microservice architecture and identify what needs to be improved.

Consulting services

Engage Chris to conduct an architectural assessment.

Join the microservices google group


Note: tagging is work-in-process

Microservices adoption   ·  ancient lore   ·  anti-patterns   ·  application api   ·  application architecture   ·  architecting   ·  architecture   ·  architecture documentation   ·  assemblage   ·  beer   ·  books   ·  containers   ·  dark energy and dark matter   ·  deployment   ·  design-time coupling   ·  developer experience   ·  development   ·  devops   ·  docker   ·  eventuate platform   ·  generative AI   ·  glossary   ·  health   ·  hexagonal architecture   ·  implementing commands   ·  implementing queries   ·  inter-service communication   ·  kubernetes   ·  loose coupling   ·  microservice architecture   ·  microservice chassis   ·  microservices adoption   ·  microservicesio updates   ·  modular monolith   ·  multi-architecture docker images   ·  observability   ·  pattern   ·  refactoring to microservices   ·  resilience   ·  sagas   ·  security   ·  service api   ·  service architecture   ·  service collaboration   ·  service design   ·  service discovery   ·  service granularity   ·  service template   ·  software delivery metrics   ·  success triangle   ·  tacos   ·  team topologies   ·  transaction management   ·  transactional messaging

All content


24 Jul 2017 » Revised data patterns