Hello, everyone. I feel like I have a use case that it is well suited to the Kafka streaming paradigm, but I'm having a difficult time understanding how certain aspects will work as I'm prototyping.
So here's my use case: Service 1 assigns a job to a user which is published as an event to Kafka. Service 2 is a domain service that owns the definition for all jobs. In this case, the definition boils down to a bunch of form fields that need to be filled in. As changes are made to the definitions, the updated versions are published by Service 2 to Kafka (I think this is a KTable?). The job from Service 1 and the definition from Service 2 get joined together to create a "bill of materials" that the user needs to fulfill. Service 3, a REST API, needs to pull any unfulfilled bills for a given user. Ideally we want the bill to contain the most current version of the job definition at the point it is retrieved (vs the version at the point that the job assignment was published). Then, as the user fulfills the items, we update the bill with their responses. Once the bill is complete it gets pushed on to the one or more additional services (all basic consumers). The part I'm having the most trouble with is the retrieval of bills for a user in Service 3. I got this idea in my head that because Kafka is effectively a storage system there was a(n at least fairly) straightforward way of querying out messages that were keyed/tagged a certain way (i.e., with the user ID), but it's not clear to me if and how that works in practice. I'm very new to the idea of streaming and so I think a lot of the issue is that I'm trying to force foreign concepts (the non-streaming way I'm used to doing things) in to the streaming paradigm. Any help is appreciated! Thanks very much for your kind attention! Simon Calvin
