So I've been part of the quest of making all Facebook social plugins faster, even if it means rewriting them from scratch. After the Send plugin, Like button (perf optimizations described here), Follow plugin, Facepile and Likebox (perf details here), now you have a faster Recommendations plugin.
The techniques used to make it faster are simple and effective: better resource packaging, reducing number of requests, inlining CSS, reducing the amount of CSS and JS by untangling dependencies, cleaning up, and sometimes simply rewriting. You can read more about these in the previous posts.
Now the results. The before-after comparison is accurate because it uses snapshots taken at the same time. This is possible because we kept an old endpoint serving the old code path. The official URL is /plugins/recommendations.php but we kept the legacy URL /widgets/recommendations.php pointing to the old code for a little while.
Before
- WPT: http://www.webpagetest.org/result/130320_JH_7BB/
- Render start: 0.854s
- Fully loaded: 1.187s
- # of requests: 15
- Total payload: 333 KB
After
- WPT: http://www.webpagetest.org/result/130320_SJ_7B8/
- Render start: 0.378s
- Fully loaded: 0.569s
- # of requests: 10
- Total payload: 48 KB
Some analysis
The total payload change is drastic. Mainly due to better packaging. And better JS modules and dependencies.
The number of requests is reduced by 1/3. Not as drastic, but not too bad either. Most of the requests are images, which is ok. They don't block anything and whenever they arrive, they are welcome. But they are not on the critical path. The reduced requests are all JavaScript. We already had a previous optimization so CSS was already inlined. But thanks to rewrites, now the HTML payload (including inline CSS) is 6.2K gzipped, down from 9.4K. Which means the initial paint can start sooner.
The initial paint (render start) now happens in half the time. And, even better, the initial paint is a complete plugin, except for the images. While before it was just a partial content. This is because CSS is here early and all JS is out of the way (async loaded, also take a peek here)
The fully loaded time is not all that important since the user has a usable list of recommendations already delivered with the initial paint. But it's still 2x faster which makes me happy.
All in all
2x faster plugin overall, 2x faster (and infinitely better) first impression. 7x payload improvement.
Making the web faster and other personal notes
Just want to take a second to mention how good it feels to be working on such high-impact performance optimizations. These social plugins are everywhere on the web. By making them faster I am fortunate to have the opportunity to make the whole web faster. Meaning make millions of sites faster, affecting the live of billions of people, every day.
What can I say, Facebook is a great place to work. The people, the impact. Every line you write matters. It's also up to you to pick what do you want to work on and where your talents and interests will have the greatest impact. And then there are the hackathons and hackamonths which means even more freedom.
I recently finished a hackamonth project, which explains why I've been silent here and on Twitter and everywhere (yet, thanks to O'Reilly folks, even though I missed a few deadlines, we were able to push this baby out the door). Let me tell you - a hack-a-month is better than vacation. Being left alone for a month to explore a completely new (to you) territory - priceless!
(Oh, if that sounds something you'd like to do, hit me up on ssttoo at ymail with your resume. FB now has engineering offices in NYC, Seattle and London, so if moving was a problem, now there are more options)
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