Cloudflare: Occasionally loading cached .js/.json files takes extremely long

We recently migrated our website to use Cloudflare.

Shortly after, many (!) users reported that the websites sometimes loads infinitely / very long.

• It happens multiple times per week.
• When it happens, it happens to a number of users, but not all.
• When it happens, the issue seems to disappear after some minutes.
• It seems to be completely depending on the network that is used to access the site. Example: When the long loading times occur on a PC that is connected to a Wifi, the issue also occurs on other devices using this Wifi. Once you disconnect your phone from the Wifi and use LTE instead, chances are it works without any problem again.

The issue happened to me like 2-3 times now, too. Loading the an .js file and a .json file seems to be what is blocking the site from loading. The .json file contains merely a few bytes, but still, it can take minutes to load.

My best guess is that it is related to Cloudflare cache.

I found this forum post, which seems to describe a somewhat similar problem. Interestingly, their server is also located in Germany: Severe problems with super slow speeds occuring since 3 weeks on all my sites when visiting from Germany Berlin

I subscribed to Pro tier of Cloudflare, just to be able to contact the customer support about this. Will keep you updated once I hear from them.

Happy about any suggestions.