The request_time in kong's access.log is much larger than the actual processing time of the upstream_response_time

[zhou-cl]

I have observed many request logs in Kong's access log where the request_time is much larger than the upstream_desponse_time. For example, upstream_desponse_time only took 9ms, while request_time is greater than 500ms or 1000ms. Most of these requests are post and put, and I don't know why or how to troubleshoot them
thank u