What is the most appropriate choice of message broker(s) and message destination(s) in this scenario?

An Order microservice and a Fulfillment microservice are being designed to communicate with their dients through message-based integration (and NOT through API invocations).

The Order microservice publishes an Order message (a kind of command message) containing the details of an order to be fulfilled. The intention is that Order messages are only consumed by one

Mute application, the Fulfillment microservice.

The Fulfilment microservice consumes Order messages, fulfills the order described therein, and then publishes an OrderFulfilted message (a kind of event message). Each OrderFulfilted message can be consumed by any interested Mule application, and the Order microservice is one such Mute application.

What is the most appropriate choice of message broker(s) and message destination(s) in this scenario?
A . Order messages are sent to an Anypoint MQ exchange OrderFulfilled messages are sent to an Anypoint MQ queue Both microservices interact with Anypoint MQ as the message broker, which must therefore scale to support the load of both microservices
B . Order messages are sent to a JMS queue. OrderFulfilled messages are sent to a JMS topic Both microservices interact with the same JMS provider (message broker) instance, which must therefore scale to support the load of both microservices
C . Order messages are sent directly to the Fulfillment microservices. OrderFulfilled messages are sent directly to the Order microservice The Order microservice interacts with one AMQP-compatible message broker and the Fulfillment microservice interacts with a different AMQP-compatible message broker, so that both message brokers can be chosen and scaled to best support the load of each microservice
D . Order messages are sent to a JMS queue. OrderFulfilled messages are sent to a JMS topic The Order microservice interacts with one JMS provider (message broker) and the Fulfillment microservice interacts with a different JMS provider, so that both message brokers can be chosen and scaled to best support the load of each microservice

Answer: B

Explanation:

* If you need to scale a JMS provider/ message broker, – add nodes to scale it horizontally or – add memory to scale it vertically

* Cons of adding another JMS provider/ message broker: – adds cost. – adds complexity to use two JMS brokers – adds Operational overhead if we use two brokers, say, ActiveMQ and IBM MQ

* So Two options that mention to use two brokers are not best choice.

* It’s mentioned that "The Fulfillment microservice consumes Order messages, fulfills the order described therein, and then publishes an OrderFulfilled message. Each OrderFulfilled message can be consumed by any interested Mule application." – When you publish a message on a topic, it goes to all the subscribers who are interested – so zero to many subscribers will receive a copy of the message. – When you send a message on a queue, it will be received by exactly one consumer.

* As we need multiple consumers to consume the message below option is not valid choice: "Order messages are sent to an Anypoint MQ exchange. OrderFulfilled messages are sent to an Anypoint MQ queue. Both microservices interact with Anypoint MQ as the message broker, which must therefore scale to support the load of both microservices"

* Order messages are only consumed by one Mule application, the Fulfillment microservice, so we will publish it on queue and OrderFulfilled message can be consumed by any interested Mule application so it need to be published on Topic using same broker.

* Correct Answer. Best choice in this scenario is: "Order messages are sent to a JMS queue. OrderFulfilled messages are sent to a JMS topic. Both microservices interact with the same JMS provider (message broker) instance, which must therefore scale to support the load of both microservices" Tried to depict scenario in diagram: