Super slow preflight OPTIONS in Chrome only

Question

I\'ve been struggling recently with a super-weird problem only happening in Chrome: as my API (NodeJS) is on a different subdomain, I need to use CORS to reach it from my front-

Answer 1

I found the solution for my case and I will share it here.

I am on Windows, using Chrome version 70, runing a AngularJS front-end with a nodeJS backend with restify on the same server. I am using fiddler to monitor the requests, and OPTIONS request can take 1 second some times, while some times just < 5 ms. Stop using Filler bring that maximum time down to 300 ms, but still considered long. And this delay happens in Chrome, but not in Firefox. I did not test other browsers.

My case might be different from the question, as I looked the Chrome network timeline, when Fiddler is present, there is a 1s waiting(TTFB) delay. And when Fiddler is not on, there is a 300 ms gap between DNA lookup and initial connection.

I finally found this AJAX query weird delay between DNS lookup and initial connection on Chrome but not FF, what is it?

Just change back-end connection URL from localhost to 127.0.0.1 and It solved my problem perfectly.