Should I be using Magento FPC and Block Cache?

Question

I am working on a Magento EE 1.11 site in which :

• A registered User can add product which appears on the respective category listing page to all (even non-logged in user).
• When user clicks on the 'Add To Cart' this button changes to 'In Cart'
• Above case also applied to the Product view page.
• This is a medium traffic site.

Now:

• Due to some customizations done by a third party vendor, the category landing page loads too slow, we have reached a limit beyond which we are not able to improve on the page load speeds anymore.
• Hence 'Caching' seems to be the way ahead. And when we enabled FPC and Block HTML cache the page load times improved.
• Now, some blocks we observed need to be 'Hole Punched' like 'In Cart' etc.

Questions:

• With the above given scenario where the user can add products means invalidating the category cache too often. Is it worth enabling FPC + block Cache and Hole punching. Will that actually give us any page load time reduction / less resource usage ?
• In general what is the criteria for deciding to enable FPC and Block Cache ?
• If FPC is enabled should I still enable Block HTML cache (I understand Block HTML cache o/p of a block but still) ?
• What pages does FPC cache (Is there a way to identify? from the full_page_cache folder) by default ?
• Are there any points I need to keep in mind when enabling FPC, what actions clear FPC.

Sorry for the type of questions, but after having read all the material my confusion has only increased. Thanks in Advance!

Answer 1

In general what is the criteria for deciding to enable FPC and Block Cache ?

Most of the type you want the all the Magento cache types On, including FPC. The case where certain Cache types or even the FPC need to be disabled all time are very rare and if you have really heavy customizations in Magento.

Due to some customizations done by a third party vendor, the category landing page loads too slow, we have reached a limit beyond which we are not able to improve on the page load speeds anymore.

I found that statement a bit troubling since caching shouldn't never be used to mask or mitigate performance problems, caching will expire and get invalidated forcing the page in questions to be regenerated.

The FPC also has some interesting quirks, for example the same category page has two cache versions depending if the customer logs in or not.

Now, I would advice to enable the profiler and start taking a look at the code that is actually slowing down the category pages. Fabrizio Branka has an excellent profiler extension that should give you more insights on the problem.

http://www.fabrizio-branca.de/magento-profiler.html

You should concentrate first on identifying the bottleneck and the bad code instead of trying to hide/mitigate the issue with caching.