WHAT IS FULL PAGE CACHE AND WHY DOES MAGENTO USE IT?
The answer the the first question is, quite literally, full page caching involves the storage of the full output of a page in a cache, so that in subsequent page loads will not require much server load at all. For high-traffic Enterprise level eCommerce sites, full page caching is imperative in order to keep server load as low as possible, and to avoid downtime during periods of high traffic. If 1000 users are visiting the site at the same time, the amount of memory used with full page caching enabled is inconsequential when compared to the server load caused by 1000 users instantiating Magento at once. Additionally, full page caching will increase site speed, since all the server needs to do is fetch and render the page from the cache. So, now that we’ve established that full page caching (henceforth FPC) is important, let’s evaluate it critically.