Ready software for failover REST api?

Question

API

Is there any ready-made software that provides a failover for http scripts (in my case, this is a callback for VK communities)?
A solution is needed that will be optimized somehow, 10k requests per second can be easy.
I assume the following scenario (from outside):
1. VK requests a callback to some FO_CB address
2. Failover software on the server receives a request to the FO_CB address and starts knocking on the API_CB address
3. When a runtime error occurs (server down, update, etc. .d.) go to step 2
4. Upon successful completion, return the response to the request from point 1.
The difficult moment is that you need to find a failover that can withstand 5 seconds of attempts to reach the endpoint.
Should I look for ready-made solutions (throw off if anyone knows) or do I need to write my own?

Answer 1

nginx+