them on the their journey with CQRS and along the way discovered confusing The CQRS journey release by patterns & practices provides real world insight. I was on a call recently with the Advisory Board for the Microsoft Patterns & Practices (P&P) CQRS Journey project where they were showing. Project “a CQRS Journey” by Microsoft (). 2 points by federicoponzi 7 github repository, journey.

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Update — clarification cqts here. The conversation got a bit derailed at that point, and I was asked how I would do it though not quite as politelyultimately leading to my tweeting this:. Anyone want to help me show them how to do it right?

Then, all sorts of other behavior are shoe-horned around those entities and… voila, a working system.

A CQRS Journey – with and without Microsoft

That is no reason to block registration from completing. I understand how people can look at systems like TicketMaster and use that as a model for this system but, once again, the differences in the domain matter. Also, attendees going to a conference together are usually coworkers, not family — there are less qualms about leaving someone behind.

This is already leading us to a model where we should not view a group registration as a single success or failure affair.

This will have an impact on the commands, events, and transactions that flow through our system. In any case where people are reserving something far in advance, there is a high likelihood of cancellations. Similar to how hotels overbook by a certain amount to offset cancellationsour conference might look at doing something similar.

The difference is that in the case of a hotel, the guest will likely just book a room in a different hotel in the case the first hotel was fully booked.

For that jourmey, we want to remember who wanted to come to our conference even when we thought we were full. You see, our best chance of joufney a jojrney that opened up due to a cancellation is by a person who wanted jokrney register before. The traditional developer thinking about systems is rooted in synchronous and sequential processes. That sounds like a pretty fair system, the only thing is that fairness was not a requirement.

While conferences, theaters, and airlines all want to have all seats filled, the difference between the ongoing models of airlines and theaters and the once-a-year model of the conference influence how sales are done. Some companies send a lot of employees to our conference so we want to give them preference in registration. It makes sense to bend over backwards for a large group, but not for a small one. A commitment from a large company tends to mean more than that from a small one.

We may have logic that decides to immediately finalize registration from Boeing and other select customers without waiting until 2 weeks before the event. So when we open registration, we can allow the first N people to bypass our waiting list and get accepted right away hourney still needing to be handled later. At that point, you can start moving new registrations through the waiting list.

The thing is that not all requirements are created equal.

We want to align the main boundaries of our software with the stable business elements. User-defined custom fields used in user-defined custom workflows, all of it appearing in reports with sorting, filtering, and grouping. You might as well give your users Visual Studio. The thing here is that we can see the collaborative nature of the domain quite clearly — multiple actors working in parallel where the decisions of one affect the outcomes of another.

Jouurney thing is that Agile Manifesto never said to intentionally cqqrs your head in the sand with regards to the purpose of the system. It was a push-back against spending months in analysis without anything but documents coming out, but the goal was to jougney a middle ground. Developers will often start arguing what the requirements are without really understanding the domain.


That is, if you allow and chose the problem to be complex. Presumably there are policies around block reservations and automatism for a point in time when excess allocations from the pools free up and are released into the global pool that then satisfies the top of a prioritized wait list.

There might be policies for reserved VIP space, discounts, and all other things. The question was — given your chosen complexity scope, how would you divide that up and how would information flow across and between those aspects of the system. For the problem definition as presented on the call, I would have gone with a simple 2-tier solution — no CQRS, no messaging, and used a Jurney storage that can scale out across multiple machines without requiring sharding Cassandra for example.

I totally agree with your statement: Sure, if you invent requirements that make little sense to the business owner, cqs can bend the architecture any way you want so that you can build the thing YOU want not necessarily what the dqrs owner wanted. Thing is, business requirements evolve. You have to live through the entire duration of a years-long project to see how the house of cards you envisioned up-front falls apart to really appreciate the value of agile and delaying ccqrs until the Crqs responsible moment.

You seem to imply that you have to decide on ALL jouurney features the system will have, up front, before you can make a coding decision.

For this reason kourney mention of them and the subsequent description of the requirements for a movie ticket system rings a bit discordant. Perhaps you should consider replacing the mention of them with a vendor such as MovieTickets, Fandango, or MoviePhone, whose primary business is movie tickets. Otherwise, excellent post, as always. If yes where can we find it? Mail will not be published required.

The conversation got a bit derailed at that point, and I cqrss asked how I would do it though not quite as politelyultimately leading to my tweeting this: We need to get into the nitty-gritty of our problem domain to find out what makes it special.

Not all registration systems are equal I understand how people can look at systems like TicketMaster and use that as a model for this system but, once again, the differences in the domain matter. First-come, first-served — fairness The traditional developer thinking about systems is rooted in synchronous jurney sequential processes.

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Command and Query Responsibility Segregation (CQRS) pattern

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