What is Varnish?
Varnish is web application accelerator. More specifically, its a 'caching HTML reverse proxy'. Let's take a second and unpack what that means and why it's awesome.

One of the features that really sets Drupal apart from other CMSs is its' filter system - the ability for Drupal to run standard text data through functions, called filters, that will alter the text in some useful way. Out of the box, Drupal 7 offers several filters by default. For example, the 'Filtered HTML' input format will run several filters, doing things like removing potentially harmful javascript, closing missing HTML tags, and adding paragraph tags where appropriate.

What's Memcached?
Memcached is a free and open-source distributed memory object caching system designed to speed up dynamic web applications by alleviating database load. It allows traditionally expensive (in terms of server CPU and RAM) database queries to be pulled from the Memcached server instead of your database. 

 
In March of 2012, one of our major goals for EmpowHER.com was to increase page load times. One of the easiest ways to accomplish that is to limit the number of HTTP requests your web server needs to fill per page request. On a CMS driven site like Drupal, the total number of requests a single page requires can easily get into the hundreds.

Fry! Stay back! He's too powerful! Oh, but you can. But you may have to metaphorically make a deal with the devil. And by "devil", I mean Robot Devil. And by "metaphorically", I mean get your coat. Why did you bring us here?

A Taste of Freedom
Oh, all right, I am. But if anything happens to me, tell them I died robbing some old man. Then throw her in the laundry room, which will hereafter be referred to as "the brig". With a warning label this big, you know they gotta be fun! Incidentally, you have a dime up your nose.

Fry! Stay back! He's too powerful! Oh, but you can. But you may have to metaphorically make a deal with the devil. And by "devil", I mean Robot Devil. And by "metaphorically", I mean get your coat. Why did you bring us here?

A Taste of Freedom
Oh, all right, I am. But if anything happens to me, tell them I died robbing some old man. Then throw her in the laundry room, which will hereafter be referred to as "the brig". With a warning label this big, you know they gotta be fun! Incidentally, you have a dime up your nose.

Fry! Stay back! He's too powerful! Oh, but you can. But you may have to metaphorically make a deal with the devil. And by "devil", I mean Robot Devil. And by "metaphorically", I mean get your coat. Why did you bring us here?

A Taste of Freedom
Oh, all right, I am. But if anything happens to me, tell them I died robbing some old man. Then throw her in the laundry room, which will hereafter be referred to as "the brig". With a warning label this big, you know they gotta be fun! Incidentally, you have a dime up your nose.

Ever wondered how you can get a record of PayPal transactions as they happen in real-time and store them in a database? What about passing along custom variables to the PayPal form, and then catching them after the payment has been completed - such as for a referral system?