A batch of rookie questions

[MightyPixel]

Hi everyone - a new Quarkus user here 👋

First I have to say that you have done great work with the documentation and the whole project looks awesome! I managed to create a Quarkus backend app sprinkled with handy extensions that reads from Kafka, gathers additional data from APIs and updates some downstream systems in reactive style. However I still have some questions that aren't clear to me:

First question: I am looking a way to control the rate of consuming from an incoming channel (in my case a Kafka topic). I saw that there is a way to limit publishing using max-inflight-messages, is something something similar? Maybe max unacknowledged (inflight) messages or max messages per second.

After reading this insightful guide I decided to try to solve the problem using Multi. This led me to:

Second question How can I consume incoming messages as Multi<Message<CustomPayload>>? So that I can control the demand of messages and consume them at a rate that is acceptable for the downstream.
I saw an example that has a field of type Multi<Double> prices; and it is exposed as endpoint, but I can't connect the dots how to make a normal Kafka consumer that reads from the stream and process them. Any examples would be welcome!

To give some context - during the processing of messages I am making requests to APIs each with different rate limiting policy and speed capabilities. I want to process all messages without dropping and if a downstream goes down to pause consumption or fail gracefully. In many articles around fault tolerance I have seen ways to act after the systems have started malfunctioning which is great to know, but I couldn't find much info on how to prevent greedy usage (lower number of requests only when something goes bad).

Third question The dead-letter-queue strategy sounds great. Are there any helpful guides on how to process messages that end up there? I was thinking of endpoint that can be used to request reprocessing of certain offsets or a special mode of the app that can be launched by a developer.

Bonus question I'm trying to use quarkus-smallrye-health extension, but I have the following problem: any additional data for checks is nested inside a data field inside each check. In order to be compliant with a standard in my company I need to basically remove the nesting and just have a flat structure in each check. Is there a clean way to achieve that? Or I'm better of implementing my own custom healthchecks?

Finally I wanted contribute an idea (maybe more if it is a good and feasible one): the quarkus dev mode is awesome. Are there any plans to incorporate something like jshell inside the Quarkus Terminal? I imagine having something like a REPL would fit great with the live reload nature of Quarkus.

If having multiple questions in single discussion isn't advised I'm happy to split them :)

Cheers!

[MightyPixel]

👋