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Domain-driven Design

by Siarhei Matsiukevich,Cloud Engineer and Go Developer at Altoros

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What is the main challenge in software development?

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How to measure application complexity❖Complexity of all interfaces that application uses❖+ Complexity of all interfaces that application provides❖+ Complexity of application source code

For me, the definition of complexity is the amount of things you should keep in mind when working with a software product.

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So, how we can deal with software complexity?❖Become a genius❖Improve the quality of source code❖Decompose your app into smaller pieces

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Different ways of application decomposition

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How to identify that decomposition is good?Loose coupling

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So what is the problem with that?

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How to identify modules?❖Based on physical layers separation❖To provide abstraction for components that CAN REPLACE EACH

OTHER

Don’t just do it because your architecture is better if you have many interfaces!

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Module identification based on physical layer separation

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Module identification based on layer abstraction

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Microservices

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Can a separate class or module be a microservice? Module should be transformed to a microservice when there is a need to scale this module independently.

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Microservices vs. monolithic apps

Category Monolithic Microservice

Understandability Hard to maintain Easy to understandDeployment Big Bang release Independent continuousTools Approved tools, languages,

and frameworksRight tool for Job

Scalability Scale everything Scale bottleneck services Project management Difficult to track More granular controlQuality Assurance Regression tests Localized testPlanning On a department level On a team level

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Domain-driven Design

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Bounded context

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An example of a ubiquitous language

public interface Customer { public void changePersonalName(String firstName, String lastName); public void relocateTo(PostalAddress changedPostalAddress); public void changeHomeTelephone(Telephone telephone); public void disconnectHomeTelephone(); public void primaryEmailAddress(EmailAddress emailAddress);}

public interface Customer { public void save(Customer customer); public void remove(Customer customer); public void findById(Integer id);}

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Microservices: team

“Any organization that designs a system (defined broadly) will produce a design, which structure is a copy of the organization's communication structure.”--Melvyn Conway, 1967

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18Don’t do it

1)Start from microservices2)Work without DevOps3)Create too many services 4)Forget to track latency

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Thank you!Want more?

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