Reverse Load Balancer: Out Balancer?

Load balancing in is a common topic, but there isn’t as much said about load balancing out. I may have an application that can prepare 1mm requests/s but is unable to send them all out at that speed because of network restraints.

Is there a concept of an out-balancer? Are there any ready-made solutions out there that can take, say, a csv of 1mm requests and distribute them across nodes and send them?

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The "Out Balancer Coordinator" could just be a queue. But that’s getting into DIY territory where I’m wondering if something like this already exists.