Command Query Responsibility Segregation design pattern

learn more… | top users | synonyms

4
votes
1answer
675 views

Distinguishing between UI command & domain commands

I am building a WPF client application using the MVVM pattern that provides an interface on top of an existing set of business logic residing in a library which is shared with other applications. The ...
1
vote
1answer
639 views

Separation versus Segregation

The term "segregation" is used in the CQRS pattern. What's the difference between segregation versus separation in this case?
5
votes
2answers
781 views

Inheritance, commands and event sourcing

In order not to redo things several times I wanted to factorize common stuff. For Instance, let's say we have a cow and a horse. The cow produces milk, the horse runs fast, but both eat grass. ...
4
votes
2answers
1k views

Distributed application using RabbitMQ

I am on my way to create an application with 4 bounded context using CQRS & event sourcing. In order to make these bounded context talk to each other I was planning on using Rabbit MQ. My ...
5
votes
1answer
2k views

CQRS + Event Sourcing: (is it correct that) Commands are generally communicated point-to-point, while Domain Events are communicated through pub/sub?

I'm basically trying to wrap my head around the concept of CQRS and related concepts. Although CQRS doesn't necessarily incorporate Messaging and Event Sourcing it seems to be a good combination (as ...
12
votes
4answers
5k views

DDD, Saga & Event-sourcing: Can a Compensate Action simply be a delete on the event store?

I realize the above question probably raises a few 'what??'s, but let me try to explain : I'm trying to wrap my head on a couple of related concepts, basically the Saga-pattern ( http://www....
1
vote
2answers
379 views

Designing a hierarchical structure with lots of reads and writes?

I am in the process of working on a video on demand system part of it involves the management of a hierarchical tree structure (think windows explorer) which allows users to upload videos, move ...
6
votes
4answers
865 views

Command-Query-Separation and multithreading safe interfaces

I like the command query separation pattern (from OOSC / Eiffel - basically you either return a value or you change the state of the class - but not both). This makes reasoning about the class easier ...
3
votes
1answer
726 views

CQRS and cache invalidation (while load balancing)

I'm slowly trying to migrate our web application to use CQRS principals. In particular, I have separated "write" and "read" interfaces into commands and queries. I have implemented a "reader" ...
8
votes
2answers
10k views

Can SQL Server and Mongo be used together?

We have a large news-oriented site that has high web traffic. The architecture is your often seen DB - Repo Layer - Services Layer - Asp.Net MVC. The problem that we've been seeing is around read ...
12
votes
3answers
2k views

Are Domain Objects in Domain Driven Design only supposed to be write-only?

I've been reading about Domain Driven Design for almost two years and have been cautiously been introducing some concepts in to my daily work or at least making plans for how things I do regularly ...
3
votes
1answer
2k views

Is there a mature, easy-to-use CQRS framework that is not Azure-specific, not outdated, or not well adopted?

I've been doing research on .net implementations with CQRS. Either everything I've seen so far is do-it-yourself, azure-specific, outdated (i think), or not well adopted Problems: Scritchy - is not ...
6
votes
1answer
1k views

CQRS without using others patterns

I would like to explain CQRS to my team of developers. I just can't figure out how to explain it in the simplest way so they can implement the pattern rapidly without any others frameworks. I've read ...
14
votes
5answers
6k views

Is it bad practice for services to share a database in SOA?

I have recently been reading Hohpe and Woolf's Enterprise Integration Patterns, some of Thomas Erl's books on SOA and watching various videos and podcasts by Udi Dahan et al. on CQRS and Event Driven ...
8
votes
2answers
4k views

Command handlers and DDD

I have an ASP.NET MVC application, that uses a query service to get data and a command service to send commands. My question is about the command part. If a request comes in, the command service uses ...
5
votes
3answers
1k views

What is the best way to scale a CQRS system?

In the previous months I have been asking a lot of questions concerning the architecture of an application I'm working on. Thanks to the answers the architectural design has changed - in fact, it has ...
5
votes
1answer
2k views

.NET CQRS Frameworks nCQRS vs Lokad.CQRS

For the last couple of weeks I've been reading up and watching any resources I can find on CQRS. I really like the concept and am keen to start delving deeper. I have only found 2 major .NET ...
3
votes
2answers
728 views

CQRS applicability when some commands need to block the UI

I am working on an app which I would dearly love to transition from a fairly traditional layered architecture to CQRS, for a number of reasons, not least fo which is that having a robust event log ...