http post request send delay

I have a http client service,somtimes it get a read time out err,and through tcpdump capture and debug, i find the service show sendtime: 2024-08-22 11:54:24.375461565 +08:00, but the tcpdump capture show arrivetime: Aug 22, 2024 11:54:28.650506000 CST, it has more than 3s interval. sometime the post packet event lost, and i can't capture through tcpdump.i want to know what cause this,can anyone help?
ps: the system has about 200k establish connection usually.
OS: CentOS Linux release 7.3.1611 (Core)
kernel: 3.10.0-1062.9.1.el7.x86_64