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Adding a bespoke controller to the design will allow the orchestration between different services to be abstracted from the back end. The controller would be responsible for splitting requests between the data providers and aggregating the responses before the reply goes back to the client.
The controller could be a micro service or, possibly, a Lambda function.
Alternative design featuring a message broker
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Rather than write a bespoke controller the, orchestration could be performed using an off the shelf product. AWS MQ supports Apache Camel and can be used to provide a sophisticated message broker service which supports multiple messaging patterns out of the box.
With our current, envisaged configuration there would be very little custom code required to be written. Most of our requirements would be handled by configurable settings in Camel.
This solution is the most flexible when it comes to adding extra services that need to be consumed.