Data replication with microservices using a messaging broker

I have a microservice based application like so:

User.Microservice – stores , user information.

Product.Microservice – stores products that user created.

Order.Microservices – stores product orders

Stack:

RabbitMQ – for Event based communication

MongoDB – for Data Storage

Each service has a public HTTP REST API.

Each service can publish and consume messages from RABBITMQ

Here is how everything communicates: current stack

Client makes a request to API GATEWAY:

lets suppose client makes a POST request to product service -> the product has user reference and other details about a product.

Well now if i want to populate product item with user details such as user’s username, the API GATEWAY should make a GET request to user service.

Here comes the data replication part i have to add the required information about user to product service.

How can i replicate user details to product service after a product is created ? And return the response to POST request along with user’s username ? if it is not present in product service…

I could use the current API GATEWAY method where the gateway calls user service , but if the user service goes down i will not have the required user details…

Somehow i need to run bus events before the response from POST request is returned…