Dominic Betts - Exploring CQRS and Event Sourcing: A journey into high scalability, availability, and maintainability with Windows Azure

978-1-62114-017-7

This document is provided "as-is". Information and views expressed in this document, including URL and other Internet Web site references, may change without notice.

Some examples depicted herein are provided for illustration only and are fictitious. No real association or connection is intended or should be inferred.

This document does not provide you with any legal rights to any intellectual property in any Microsoft product. You may copy and use this document for your internal, reference purposes. You may modify this document for your internal, reference purposes

2012 Microsoft. All rights reserved.

Microsoft, MSDN, SQL Azure, SQL Server, Visual Studio, Windows, and Windows Azure are trademarks of the Microsoft group of companies. All other trademarks are property of their respective owners.

The project is focused on building highly scalable, highly available and maintainable applications with the Command & Query Responsibility Segregation and the Event Sourcing patterns.

The project was positioned as a learning journey. This guidance is designed to help you get started with the CQRS pattern and event sourcing. It is not intended to be the definitive guide to the CQRS pattern and event sourcing. Instead, it's a journal that describes the experiences of a development team with no prior CQRS proficiency in building, deploying (to Windows Azure), and maintaining a sample real-world complex enterprise system as a reference implementation (RI) to showcase various CQRS and ES concepts & techniques. The development team did not work in isolation; we actively sought input from industry experts and from a wider group of advisors to ensure that the guidance is both detailed and practical.

The CQRS pattern and event sourcing are not mere simplistic solutions to the problems associated with large-scale, distributed systems. By providing you with both a working application and written guidance, we expect you'll be well prepared to embark on your own CQRS journey.

This written guidance is itself split into three distinct sections that you can read independently: a description of the journey we took as we learned about CQRS, a collection of CQRS reference materials, and a collection of case studies that describe the experiences other teams have had with the CQRS pattern. The map below illustrates the relationship between the first two sections and our main milestones.

This is another excellent guide from the patterns & practices teamreal software engineering with no comforting illusions taken or offered. This guide provides a detailed journal of the practitioners implementing a real production system using the CQRS and Event Sourcing patterns, and also highlights the tradeoffs and teaches the principles that underlie them. The topics presented are relevant and useful, especially if you are building highly scalable Windows Azure applications. Youll be both challenged and inspired!

Scott Guthrie, Corporate Vice-President, Azure App Platform, Microsoft

Having participated and co-authored various guides from patterns & practices, the "CQRS Journey" follows the same walkthrough, scenario-based style, but adding even more fresh empirical content. It's a true testament of a skilled development team without previous CQRS experience, going through the journey of implementing a complex system and documenting their adventures and lessons learnt in this diary. If I had to recommend to someone where to start with CQRS, I would definitely point them to this guide.

Matias Woloski, CTO, Auth10 LLC

The "CQRS Journey" guide is an excellent resource for developers who want to begin developing a CQRS system or convert their current system. Its a true trial by fire approach to the concepts and implementation hurdles that a team would encounter when adopting CQRS. I would recommend reading it twice as I picked up even more lessons the second time through.

Dan Piessens, Lead Software Architect, Zywave

I think its a really big step in communication with the developer community. You not only share your development experience with a broad audience (which is very valuable by itself) but youre also open for learning from the community. While working on real projects its difficult to stop, find some time to structure your knowledge, prepare it in the form understandable for others. Its very cool that you found time and resources for such educational effort, I really appreciate this.

Ksenia Mukhortova, Business Applications Developer, Intel

Im very excited about A CQRS Journey for a number of reasons. It explores, with an even hand and a fair mind, a topic where opinions are both diverse and numerous. True to its name, the guide captures the progression of learning. Conclusions are not simply stated; they arrive as a result of experience. Additionally, the project embraced a passionate community with a spirit of inclusion and transparency. The result is friendly-to-read guidance that is both diligent in execution and rigorous in its research.

Christopher Bennage, Software Development Engineer, Microsoft

The journey project used Windows Azure SQL Database (backing write & read models), Service Bus (for reliable messaging), and Tables (for event store). Production-quality, scalable cloud services that can be provisioned on-demand with a few mouse-clicks (or API calls) can turn some tough infrastructure problems into trivial ones.

Bill Wilder, MVP, Independent Consultant

Perhaps the best lessons out of this guidance will be just how easy it is to work with Microsoft now that they are embracing more community and open source.

Adam Dymitruk, Systems Architect

The work that patterns & practices is doing here is very important as it is packaging the concepts in a digestible fashion and helping developers to wade through the ambiguities of CQRS. The real world experiences captured within the journey project will be invaluable to folks looking at applying CQRS within their application development

Glenn Block, Senior Program Manager, Microsoft, Windows Azure SDK for Node.js, Organizer at ALT.NET Seattle Chapter

The p&p teams dedication and hard work go hand-in-hand with the very high level of competency present on the team. Their attention to detail, insistence on clarity, and open collaboration with the community all led to the creation of material representing enormous value to consumers of the guidance. I definitely plan on referencing this material and code in future engagements because I think my clients will derive many benefits from ita win-win for everyone!