httpKeepAliveTimeoutSec

Specifies how long to keep a connection open, after completing a response, while there is no matching traffic (in seconds). If an HTTP keepalive is not specified, a default value will be used. For Global external HTTP(S) load balancer, the default value is 610 seconds, the minimum allowed value is 5 seconds and the maximum allowed value is 1200 seconds. For cross-region internal HTTP(S) load balancer, the default value is 600 seconds, the minimum allowed value is 5 seconds, and the maximum allowed value is 600 seconds. For Global external HTTP(S) load balancer (classic), this option is not available publicly.