CQRS / context communication / eventstore / push or pull?

Question

The relationship between the restricted context in the CQRS / ES architecture is achieved through events; context A generates events as a response to commands, and these events are then redirected to context B via the event bus (message queue).

Or ... you can save events in an eventstore (belonging to context A). Or ... both (save and forward).

My question is: from context B, should events be pulled from the context store? or just consume events that have passed through the event bus?

I am leaning towards a pull-up approach. Because then we can make some catch-up in context B. On the contrary, in an sensible approach, context B may not be aware of the events that were delivered when B experiences downtime.

So ... does that mean ... when we have an eventstore, can we just forget about the message queue (seems redundant)?

Or am I missing something?

Answer 1

You want to view Use event stream without Pub / Sub

At the DDD Europe conference, I realized that I spoke with speakers where (sic) avoids Pub / Sub whenever possible.

The following discussion may make a difference. TL DR: not many pub / sub fans.

Conrad Garus on Push or Pull? describing the Pull project:

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