Web Site Optimization: FrontEnd and BackEnd

A lot of talks on this conference was focusing on what is called “FrontEnd”. The meaning of Frontend is not the frontend web server commonly used in many architectures but rather optimization on the client side - how to make a browser to do less requests, make them parallel, fetch less data and execute client side code faster.

Steve Souders mentioned in his talk for Alexa 10 web sites he examined typically 80-90% of page response time comes from other things than fetching HTML of the main page - fetching CSS, JavaScript, Images which makes it number one thing to focus your optimization on.

I do not fully agree for number of reasons.

First - a lot of people focus on Backend optimization first, have monitoring and graphing setup based on the main HTML page response this means quite frequently we speak about sites which have relatively well optimized backends but have not spent time on the frontend optimization. In this case not a big surprise there are more low hanging fruits on frontend part. We often deal with people with less than optimized backends with some pages (search,reports etc) taking minutes to load which makes these few seconds you can shave off by client side optimization secondary.

Second - The stakes for backend optimization are higher. If you do not optimize your web site on Frontend you will have worse user experience - users may not engage so actively, leave your site faster or not convert. This is very important. However if you do not optimize backend enough to handle your load your web site can simply get

overloaded and die. Remember all these “slashdotted” or “techcrunched” sites which went down because their back end just was not ready.

Third - Even if your backend is reasonably fast say you can have under 100ms response time on main HTML page there are still reasons to optimize it, especially for large scale systems. If you can come up with idea to provide same response time just with lower hardware requirements you can save on hardware, power and operations which are considerable costs for large projects.

I would say instead the same rule as back end optimization applies here - if you spend 90% time running PHP code and only 10% fetching data from MySQL database it does not make sense to focus on MySQL optimization. If 90% is spent on other tasks than fetching your HTML page all together you surely should focus on it. But get real numbers for your application before you decide.

Having said that I will now go and read Steve’s book which he kindly signed for me to get up to speed with front end optimization.