Example with redis (using https://github.com/bcoe/crapify)
./crapify start --port 7070 --speed 1000
Let this port forwarding the redis through the proxy:
socat TCP-LISTEN:6381,reuseaddr,fork PROXY:localhost:redis:6379,proxyport=7070
And connected to redis
redis-cli -p 6381
When i get some big payload after some idle time it was coming fast, however if i repeated the GET command in redis (with a very small interval), it would be slow (2 ~ 3s delay)