Microservices are an architectural style where applications are composed of small, independent services that communicate using lightweight mechanisms like HTTP. Each service focuses on doing a small, well-defined job and is independently deployable. There is minimal centralized management of services, which may use different programming languages and data stores. While microservices provide benefits like flexibility, they also introduce challenges around performance, asynchronicity, failures, and complexity. Microservices represent an implementation choice governed by enterprise architecture principles, not dictated by EA. They differ from SOA in areas like synchronous vs. asynchronous communication and ceremony levels.

1. Microservices and their fraught
relationship with EA and SOA

2. what is a microservice?

3. “ … the microservice architectural style is an approach to developing a
single application as a suite of small services, each running in its own
process and communicating with lightweight mechanisms, often an
HTTP resource API. These services are built around business
capabilities and independently deployable by fully automated
deployment machinery. There is a bare minimum of centralized
managementof these services, which may be writtenin different
programming languages and use different data storage
technologies.”
James Lewis, 2014 (emphasis mine)

4. (James Lewis)

5. small problem domain
encapsulated
loosely-coupled/independent
upgradeable/replaceable/disposable

6. microservices
continuous
delivery
dev/ops
capability-based,
multi-disciplinary teams
automated deployment
containers
its own process

7. PRO
deals with logical complexity
flexible development & deployment
“fits in my head”
composable
replaceable
decoupled scaling

8. CON
performance
asynchronicity
eventual consistency
cascading failures
operational complexity
granularity

9. (James Lewis)

10. EA and microservices
service-based business – it’s fractal
capability-based – “bounded context”
service containers – “define component boundaries”
service contract – “published interface”
architecture principles – “define guiding principles”
operating model
software containers

11. microservices are an implementation choice
microservices are a development paradigm
microservices are governed by EA, not decided by EA

12. Business Process Layer
ESB
Integration Layer
where microservices play
Construction Layer
© Fragile to Agile
}SOA

13. SOA and microservices
synchronous vs. asynchronous
smart pipe vs. dumb pipe
high ceremony vs. low ceremony

14. (James Lewis)
remember this?
how different does it sound to the SOA premise?
are microservices just “SOA done right”?

15. Reading
• James Lewis (Thoughtworks) & Martin Fowler
http://martinfowler.com/articles/microservices.html
• Michael Brunton-Spall (GDS, Guardian)
http://www.brunton-spall.co.uk/post/2014/05/21/what-is-a-microservice-and-why-does-
it-matter/
• Dan North “Microservices: software that fits in your head”
https://speakerdeck.com/tastapod/microservices-software-that-fits-in-your-head
• Jeppe Cramon, TigerTeam
https://www.tigerteam.dk/2014/micro-services-its-not-only-the-size-that-matters-its-
also-how-you-use-them-part-1/ (five-part series)