Exploring CQRS and Event Sourcing

by Dominic Betts, Julian Dominguez, Grigori Melnik

This guide is focused on building highly scalable, highly available, and maintainable applications with the Command & Query Responsibility Segregation and the Event Sourcing architectural patterns. It presents a learning journey, not definitive guidance. It 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 to showcase various CQRS and ES concepts, challenges, and techniques.
The development team did not work in isolation; we actively sought input from industry experts and from a wide 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.

Genres: Programming, Technology, Software, Technical, Architecture, Computer Science

346 pages, Kindle Edition

First published October 1, 2012

Reviews

[Ahmad hosseini · Rating 3 out of 5]

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 the underline them.
This guide is a good resource for developers who want to begin developing a CQRS system or convert their current system.
Reading this book showed me that CQRS and ES was not as hard as I thought. CQRS pattern appears to be simple in practice, it requires a significant shift in the way you think about many aspect of the project.

[Pawel Dolega · Rating 3 out of 5]

This is a little awkward book. As stated pretty early on - it's a journey toward implementing CQRS / Event Sourcing / DDD strategies during implementation of a sample application. You need to read it while closely following the code (OK, you don't need to but it helps, at least in certain sections). But here is a catch - it's not always that easy, because - as the word "journey" implies - particular chapters in the book does not always really refer to the actual code you find in repo (well, it refers to the state of the code at some point, however - contrary to initial intuition - not always to particular tag indicating version of the system described in the book).

On top of this it's also very closely tied to MS Azure and it's services (storage, queues). Therefore it's not a very digestible reading for someone not accustomed (or not that much interested) in these MS technologies.

Still, the book has value. If you are from MS world - it is probably straightforward reading. If you are for instance like me - mostly from Scala world these days - your eyes will bleed because of all this boilerplate. If you however overcame initial repulsion, there are really good insights in the book. Especially if you know a little bit about CQRS, ES, DDD but would like to see some real implementations - this might be a good source.

[Tomek Lelek · Rating 4 out of 5]

A very practical book, but the use cases are for small traffic and low scale.

[Chris Wong]

This book has a good intention but poorly executed. It feels like there is no editing or no inputs from a good editor. First of all, as the authors are telling the journey of learning CQRS and Event Sourcing, the authors interleaves numerous and repetitive notes to remind the readers that "this is a journey and the implementation is evolving, the final implementation will change", etc. I can appreciate that extra clarify but it's really quite implicit by the word "journey" and any software developer would understand that it's evolving especially when you're telling the journey of this learning experience. Secondly, repetitive notes are interrupting the flow of reading the journey. If the author's goal is to have readers submerge into their experience and learn from it, they've completely destroyed the flow and failed.

Another similar problem is the interjected "notes" to introduce Microsoft technologies and direct readers to read more about it in the Reference section. This happens so frequently that I want to throw the book out the window. If you're gonna tell a story, tell the story. Don't stop every minute and make an 20 seconds advertisement. It's just too annoying.

I want to like this book but 20% into this book and I'm feeling strongly that it's a waste of time. The whole book can probably be summed up in less than 50 pages.

[Saphyel · Rating 4 out of 5]

Explains very well the concepts of CQRS and Event sourcing (and a bit of DDD), their examples are with M$ products (kind of obvious or expected?) but feels more like a choice of preferences rather than just marketing/spam.

I usually skip the the real case scanarios but in this case I highly recommend to read them because every case is different and if you are planning to start to use this technique you may follow one of their approach

[Andrew Gapic · Rating 4 out of 5]

Very informative book in terms of building systems with CQRS/ES. The gems were really the conversations between developers and the quotes. A bit aggressive when it came to pitching MS problems, but it's forgivable.

[Tom · Rating 2 out of 5]

Stopped reading, way of writing is not really my cup of tea for a book and wasn't motivating me to keep on reading.

[Marko Kunic · Rating 4 out of 5]

Its nice to read about peoples journeys with CQRS and ES. Book talks about how they evolved their application with multiple versions, how they delt with common problems and what they did to solve it.