If your site's contents constantly change, forget caching. It will cause more problems than really speeding up the site. My suggestions:

1. Pagespeed (with moderate optimization, over optimization will cause a lot of headaches)

2. CDN to host your script, css and images files

Hi Mark, yes it was causing more problems then performance in the past for us, if i well understand we should disable the joomla cache option and module ?

We have nGinx server as reverse and the performance is better.

Module is fine but it also depends on what kind of modules. If the module changes very frequently (daily, hourly, etc) then it would be quite pointless to cache the module.

Example scenario of bad caching on module:

Online users module is not ideal to be cached if your login / logout frequencies are high. Imagine this, when a cache happens, there is more performance used on the initial page load to cache. If your login / logout frequencies are high, then the system would practically need to cache again each time a user logs in which defeats the purpose of caching the module in the first place.

Having said the above, if your login / logout frequencies are low, then it would be useful to cache. Assuming that an average login / logout would be between 5 - 10 users daily, you are leveraging between caching about every hour, which is fine

All of these caching strategies are very well dependent on your site activities and it differs from site to site.

Thanks Mark, i mean the joomla system cache PLUGIN not module sorry,
We cant check modules one by one and activate or not cache for each one, i think we'll disable cache option and plugin to avoid any bugs (sessions etc.)

I guess i am not alone to ask about performance here, maybe you can post a blog article in futur about all best practices for SI extensions users

have a great week end guys!

All of this is still very relative to what you do with your site. The basic rule of thumb is if your site has heavy changes / activities, forget about caching altogether.

I doubt Facebook runs any cache on their activities HTML at all. Probably only certain portions where they are static and don't change often.