Command-Query-Responsibility-Segregation

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The following should be improved: The introduction does not show what the variant formation consists of. The reader does not understand the advantages and disadvantages because they are not justified.

Functional principle of CQRS with event sourcing

The Command-Query-Responsibility-Segregation ( CQRS , [ kə'mæ: nd 'kwɪ (ə) ri: ri, spɑnsə'bɪləti, sɛgrɪ'geiʃ ( [ ) n ] or [ si: kju: ɑ: r s ] , English for about command-query-responsibility separation ) is a variant of the CQS principle on database queries, which was defined by Greg Young .

advantages

• High scalability
• Suitable for use in service-oriented architectures , for example in cloud computing
• Write and read access can be scaled independently of one another
• Improved security thanks to separate roles for read and write operations
• Simultaneous use of different versions of the same software is possible
  • Maintaining backward compatibility possible
  • Migration to the new version in live operation possible without downtime
• Adaptability to changed business requirements
• Development of the individual components by different teams
• Can be combined with event sourcing

disadvantage

• High effort in software development. More suitable for projects with many simultaneous users.
• Requires the right infrastructure.
• Transactions are difficult to implement.
• Queries can be carried out before commands have been carried out. Versioning and an in-memory cache are therefore required to ensure that the client receives data in the correct version.

Trivia

The abbreviation CQRS is by software developers because of Google - AutoCorrect jokingly as cars [ kɑrz spoken].

Frameworks

.NET

• Tyrone Groves: SimpleCQRS. In: GitHub. Retrieved July 21, 2014 . 
• The Ncqrs Framework. In: GitHub. Retrieved on July 13, 2014 (English, CQRS framework for the .NET framework ). 

JVM

• AxonIQ. Retrieved March 10, 2020 (English, CQRS framework for the Java runtime environment ). 

JavaScript

• wolkenkit. Retrieved June 27, 2017 (English, CQRS, DDD and event sourcing framework for JavaScript). 

PHP

• prooph. Accessed February 1, 2018 (English, CQRS and Event Sourcing Infrastructure for PHP). 

literature

• Chris Richardson: Microservices Patterns . Manning, Shelter Island NY 2019, ISBN 978-1-61729-454-9 , pp. 228-252 (American English).

Web links

• CQRS Journey. In: patterns & practices, MSDN. Microsoft, July 2012, accessed on July 13, 2014 (English, Tutorial on CQRS and Event Sourcing in C # ). 
• Kanasz Robert: Introduction to CQRS. In: CodeProject. March 21, 2013, accessed July 13, 2014 (English, Introduction to CQRS in C # ). 
• Greg Young: CQRS / DDD by Greg Young. In: YouTube. Rinat Abdullin, January 20, 2012, accessed on July 13, 2014 (English, Introduction to CQRS and DDD ). 
• Lev Gorodinski: Domain-Driven Design, Event Sourcing and CQRS with F # and EventStore. In: YouTube. DC F # Meetup, March 6, 2014, accessed July 13, 2014 (English, CQRS and EventSourcing in F # ). 
• Golo Roden, Matthias Wagler, Susanna Roden: wolkenkit - The semantic JavaScript backend for event-driven development . Accessed July 9, 2017 (PDF, English, introduction to CQRS, DDD and event sourcing)

swell

1. ↑ Martin Fowler: CQRS. July 14, 2011, accessed May 18, 2014 . 
2. ^ Greg Young: CQRS Documents by Greg Young. (PDF) In: WordPress. November 2010, accessed July 13, 2014 .