event-sourcing

I have a question regarding projections involving multiple aggregates on a CQRS architecture. For example sake, suppose I have two aggregates WorkItem and Developer and that the following events happen sequentially (but not immediately) WorkItemCreated (workItemId) WorkItemTitleChanged (workItemId, title) DeveloperCreated (developerId) DeveloperNameChanged (developerId, name) WorkItemAssigned (workitemId, DeveloperId) I wish to create a projection which is as "inner join" of developer-workitem: | WorkItemId | DeveloperId | Title | DeveloperName | ... | |------------|-------------|--------|----

I am trying to store domain events in a postgres database. I am not sure in many things, and I don't want to redesign this structure later, so I am seeking for guidance from people who have experience with event sourcing. I have currently the following table: domain events version - or event id, integer sequence, helps to maintain order by replays type - event type, probably classname with namespace aggregate - aggregate id, probably random string for each aggregate timestamp - when the event occured promoter - the promoter of the event, probably user id details - json encoded data about the

I'm struggling to get my head around what should happen when rebuilding the model by replaying events from the EventStore, in particular when events may trigger other events to happen. For example, a user who has made 10 purchases should be promoted to a preferred customer and receive an email offering them certain promotions. We clearly don't want the email to be sent every time we rebuild the model for that user, but how do we stop this from happening when we replay our 10th PurchaseMadeEvent ? Events chaining can be very tricky and easily run out of control, so I'd avoid it as much as

Let's take a simple "Account Registration" example, here is the flow: User visit website Click "Register" button and fill form, click "Save" button MVC Controller: Validate UserName uniqueness by reading from ReadModel RegisterCommand: Validate UserName uniqueness again (here is the question) Of course, we can validate UserName uniqueness by reading from ReadModel in MVC controller to improve performance and user experience. However, we still need to validate the uniqueness again in RegisterCommand , and obviously, we should NOT access ReadModel in Commands. If we do not use Event Sourcing, we

That is meant to be read as a dual upsert operation, upsert the document then the array element. So MongoDB is a denormalized store for me (we're event sourced) and one of the things I'm trying to deal with is the concurrent nature of that. The problem is this: Events can come in out of order, so each update to the database need to be an upsert. I need to be able to not only upsert the parent document but an element in an array property of that document. For example: If the document doesn't exist, create it. All events in this stream have the document's ID but only part of the information