Slow Loading Time At Product Detail Page

[leotest]

A e-shop has developed and put to the three server:

 

the first 2 is amazon, should be same setting

 

Server 1:

http://be-pure.com/en/women/3-slim-y-tank.html

 

Server 2:

http://52.77.216.83/en/women/3-slim-y-tank.html

 

the last one is just local hosting

 

Server 3:

http://internal001.zizsoft.com/be_pure/en/women/3-slim-y-tank.html

 

The problem is server 1 loading very slow compare to the other two server, but the performance should be the best among 3. It looks as if server 1 hasn't cache

 

but in fact, all of them has 

 

turn on smarty cache, using file system , with recomplie when modify

and 

turn on the file system cache

 

Given that the code and server setting are the same among three server , How to debug/ check whether the perstashop is using cache? And what takes the long load time for server 1?

 

Thanks a lot

[tplmika]

Go test with this tools : https://varvy.com/pagespeed/