Slow loading at certain circumstances

Hello @everybody

I have a problem with loading times but only at certain circumstances and I can't figure it out atm which makes me really concerned. Why "concerned" - because ZC is my "how to create a blazing fast E-Commerce Shop"...

It normally loads from home, from webpagetest always crazy fast.
At my storage the mobile connection is a bit worse but not bad.
What I see is a strange behaviour. At the storage the ZC Shop needs a long time to start loading, while static sites and Shopware Sites ehich are on the same server load immidiately (and as fast as you would expect from a slower mobile connection).

First I thought it would be mobile connection, then I thought it could be worse ipv6 handling. But nothing could be proven.
Just the ZC shop needs a long time to initialize.
Could it be anything with the AJAX code?

The url is https://www.roller-aus-blech.de

First of all, congrats on a Lighthouse score of 97, 97, 100, 100 for desktop and 81, 97, 92, 98 for mobile. BTW, always test from an incognito connection for more accurate results.

Your site shows 1.0 seconds for the desktop to load from here in the Texas Hill Country. The mobile is not so good at 3.7 seconds. Lighthouse can point out to you where you need to improve.

Of course, I am on a 500Mbps fiber hookup. It's like having the Autobahn but, as you know, even the Autobahn can get a traffic jam.

Houston has a portion of freeway that is known as the Katy Freeway. With 12 main lanes, 8 feeder lanes, and 6 managed lanes for a total of 26 lanes (13 in each direction)! At certain times of the day, it is bogged down to 10 mph or slower.

The point is - at almost 4 times slower, the mobile is always going to be slower than desktop. And, anything in between your location and your server could be the real cause of a slow down. As to the difference between ZC, static, and Shopware; I'd guess that ZC is loading a lot more data. Especially versus a static site.

There are ways you can trace the route to your server from your location (Windows calls it tracert and it is used from a command prompt). Often, you'll see a line in a tracert that says Request timed out. This means your travels down the internet Autobahn had to take a detour.

If the tracert does not finish, the "road" is totally blocked somewhere between you and your server. Note that, sometimes, the tracert to two or more sites on the same server might use more than one "route" to get to the server.

The best you can do as a store owner is to address all the Lighthouse suggestions and hope a detour or blockage doesn't create a "traffic jam".

Thank you very much for your detailed insights.

I 'm going to take my notebook to the storage and make a traceroute via mobile hotspot.

I only can describe how it feels at the moment. And it is like there was an wait on I/O at the server, which isn't the case. I know the status of the server very well and I know about CPU to I/O to network relations. I did a lot of stress test in the past.
I also tested from Frankfurt (which is 200 miles away) with older mobile devices and slower connections too. It's fine when it takes longer to load on slower connection.

At the storage my ZC shop takes 5 to 10 seconds estimated to start loading (as if there would be a DNS resolving issue). You see the layout (which probably is cached) and the loading bar at the left not moving. Then after lots of seconds it starts and finishes the loading at regular speed.
I load one of the static sites just to check if there was a general connection problem with either my phone connection or the connection at the Data Centre. They load perfectly quick.
The Shopware shop is much heavier in data assets and requests. But it starts loading immidiately (as expected) too (because of mobile connection slower of course).

I'm running the most recent German ZC version 1.5.7f with PHP 8.0.29 (I haven't noticed these issues with 1.5.0, 1.5.3 or 1.5.5f)
I was able to reproduce this issue at another day.

I don't have that many insights into zen-cart and its session cookies, jquery and CDATA and Ajax and so on.

I 'm going to investigate further.
I really have no idea. But there's something not as expected.

some update (I haven't been able to make test with laptop yet)

At my storage from mobile ZC needs 13 seconds to start loading
With Cache additional 2 seconds to finish.
Without Cache additional 12 seconds to finish.

The Shopware Shop takes about 2 seconds to fully load (as expected [or even better]).

There's plenty of CPU free.
There's no wait on IO.

So what the heck?

Some new infos:

what i was able to exclude as errors are:

- PHP version
- hosting
- connection
- device

What I assume is a webserver configuration at .htaccess

I have several subdomains for testing and these vanilla ones normally are slower but in this case it is the opposite.

It looks I got it.
I'm using several deny IP entries within the .htaccess

Without these ones it's working as expected.
I don't know why max. 50 deny IP entries would cause that.

Very curious that this issue is only at mobile connection.
And no issues from external testings.