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I am working in a web app which implements backend in event sourcing. Event sourcing has given us great power to go back in time, run projections to get different types of reports. Also, we can potentially build our database from scratch by replaying the projections if we need to.

We have certain modules which do not give much analytical value by implementing event sourcing in it. For example, a questionnaire creation, which is nothing but a simple form CRUD. We have event sourcing in it, but the only advantage we potentially have from that is to rebuild the forms database from the stored domain events. Or to get values like how much time a user took to make the questionnaire etc.

But still those analytics do not give us much info because the state change in a form is not as valuable as other parts of the system. Like e.g. changing state of a bank account through domain events give us much more information as compared to a changing state of a form CRUD.

How do you guys approach such situations and know if a certain part of the app is good for event sourcing or if it is an overkill?

Mihir Bhende
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Whether or not it's overkill is a matter of opinion, but CRUD (or really CUD, since a read isn't a meaningful event) events (e.g. WidgetCreated, WidgetUpdated, WidgetDeleted; especially the WidgetUpdated) can be a sign of an anemic domain.

Assuming that each update is atomic in your DB, you can likely get the same results (a stream of events for other components to consume) by using change data capture (e.g. Debezium for many SQL DBs to put a change feed into a Kafka topic, or some DBs like Azure Cosmos offer a native change feed) to capture changes to records in the DB.

Event sourcing now with CRUD events does give you the flexibility to flesh out the domain model later if requirements change. That requires a sense of how likely (and when...) the requirements are to change in a way that makes richer domain events handy vs. how much effort you're expending in event-sourcing now.

HappyTown
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Levi Ramsey
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  • Thank you @Levi, That makes much more sense and gives a new perspective to look at this situation. Using Debezium to be a product of events is a great idea. I will whiteboard the domain logic and see possibilities of the model requirements being changed. – Mihir Bhende Oct 04 '21 at 21:46