How can I increase max concurrent request of Phoenix on fly.io?

I made a toy project that provides a simple API for testing.

https://json.media/test_api

This project is served via fly.io.
Here is my fly.io configuration below. I configured services.concurrency.hard_limit to 10000 and services.concurrency.type to requests following max concurrency can not be greater than 300 - #4 by fxsjy.

I wanted to do a load test for this project. Below is the code I used for the load test.

When I run the code that tests with req, about 200 requests returns ok and other requests returns error %Mint.TransportError{reason: :closed}.

How can I increase max concurrent request over 200?

These kinds of load tests are hard. We won’t allow that many requests from a single IP address. So the app may not be the bottleneck.

To do a proper load test, you’ll need to generate traffic from multiple sources in multiple regions.

Or, if you want to test your app directly, run a load test over the private network directly against its IP.

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