Thank you for your quick response.
It may be caused by https. The benchmark for http://$myapp.fly.dev works well, however, if I replace “http” with “https”, the server can only serve at most 200 concurrent connections.
Try changing the concurrency type to requests. Connections concurrency means our proxy is opening a new connecting to your VM each time. nginx does not like that and tends to behave better when we pool connections.
This is expected behavior — there’s concurrency limits on TLS handshakes (max concurrent handshakes per IP). You’ll need to spread your test across several IPs to make it look more like organic traffic to get meaningful numbers.