All posts tagged CQRS

Part 1 – Microservices: It’s not (only) the size that matters, it’s (also) how you use them
Part 2 – Microservices: It’s not (only) the size that matters, it’s (also) how you use them
Part 3 – Microservices: It’s not (only) the size that matters, it’s (also) how you use them
Part 4 – Microservices: It’s not (only) the size that matters, it’s (also) how you use them
Part 5 – Microservices: It’s not (only) the size that matters, it’s (also) how you use them

As I explained in Microservices: It’s not (only) the size that matters, it’s (also) how you use them – part 5, to me a service is a logical boundary that is the technical responsible for a given business capability.
This means that the service owns all data, logic and UI for this capability everywhere it is used.

What does it mean that a service is a logical boundary?

As explained in Philippe Kruchten’s 4+1 view of software architecture, we should not automatically force the logical view to be the same as the physical implementation or for that matter the deployment view.
This often means that a service isn’t a single implementation or deployment artifact.

Examples of business capabilities are: Sales, Shipping, Marketing, Billing, Policy Management, etc.
These capabilities are pretty broad in their scope. You’ve probably read that a microservice should follow the Single Responsibility Principle (SRP) – it should do one thing and do it well.
But if a microservice should cover an entire business capability it would most like be fairly big, which goes against many of the qualities we like about microservices, such as:

  • Small (easy to comprehend)
  • Replaceable (discard the old and write a new in 2 weeks)
  • Upgradable (upgrade just the parts you want without interrupting other parts)
  • Fast startup/shutdown
  • Individually deployable

A large service is still individual deployable, but from a scaling point it’s typically all or nothing: either you scale the entire deployable unit or you don’t.
What if it is only certain use-cases that needed scaling? This is often harder with too big a deployable unit (what some people refer to a monolith) due to individual components inside the unit being too tightly coupled, like a tangled ball of yarn.

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The slides from our AANUG talk on “Agile, Architecture, DDD and CQRS” is available here

As always, feel free to leave comments 🙂

The slides from my recent AANUG conference talk is now available on Slideshare:

As always, if there’re any question or comments leave them below and we’ll get back in touch.

Most companies today use SOA to integrate their systems or mobile applications, or do they?
Join me on a historical trip where we will see how integration has remained stuck in the same patterns and we will also take a look at the emperors new clothes (or SOA as it’s practiced today).
After this we will look at how to do SOA better and the principles that will make this transition possible (keywords: Event Driven Architecture, Domain Driven Design, Composite UI’s and CQRS)

You can find the slides and video here.
Slideshare version of the slides is available here

If you have comments please post them below 🙂


Saying that you’re a .NET shop, a Java shop or some other programming platform shop is just as ridiculous as if a software tester is saying that he is just a BDD man. Hopefully he is much more than that and has a more balanced approach to software testing, so he can select that test approach that makes the most sense for the problem at hand. Wouldn’t you be worried if you went to your car repair shop and were told that they’re only a piston shop?
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