Start server

./gradlew run

Run

ab -c 1 -n 200 localhost:8080/proxy

to warm up the app, all should be fine. Now run

ab -c 5 -n 200 localhost:8080/proxy

and a few, normally 4, requests failed. If u run

curl localhost:8080/i

u will see that all (400) requests has arrived at the "server".