Stop Guessing: Diagnosing and Fixing WordPress Performance

Presentation by Matt Kopala at WordCamp LA 2018

Speed matters. People are impatient. If your website or a client’s website doesn’t load quickly – within a just a couple of seconds – many visitors will abandon it completely. A slow site means lost time & revenue. But figuring out how to speed up a slow site can be HARD.

Everyone’s got a suggestion and an idea for how to fix your performance issues. Disable this plugin, try this, try that … usually just guesses, and not based on real data.

STOP GUESSING. If you have a performance issue, or just want to make your site faster, you need to KNOW exactly what is going on with your actual, live site in production.

We’ll start by with an overview of WordPress page performance, and then focus on server response times, and what affects them. We’ll take a look at tools that will tell you exactly what plugins are slowing down your site.

Why performance matters

wastes time if wp admin is slow
Google ranking
visitor perception
speed = happiness
Why don’t developers fix their slow site
Optimization can be risky and uncertain
priority = value / effort

Caching

Is caching the solution?
A good object caching plugin can help across pages
Page caching failures
- Doesn’t work on wp admin
- Large sites with too many pages
- Caches expire, get cleared
Caching is great, but is only part of solution

Measuring site performance

Anatomy of a page load
- TTFB - Time to first byte
  - DNS
  - https
  - Server response
    - WordPress php and sql queries
- Parsing
- Asset download js, css, images, fonts
- Rendering
How fast time to first byte TTFB
- Very fast 50-150 ms
- Fast 150-300 ms
- Good 300-500 ms
- Very slow 1.5 sec

Diagnosing server response time (TTFB)

Page performance - Chrome Web Store
Chrome developer tools
- Get Started with Analyzing Network Performance in Chrome DevTools
- Get Started With Analyzing Runtime Performance
WebPagetest - Website Performance and Optimization Test
- TTFB
- Load time
- Film strip view shows over time how page looks as its loaded
GTmetrix | Website Speed and Performance Optimization
- Not recommended. I like stat for total page size. Is it accurate?
SiteDistrict
Recommended WordPress hosts
- Kinsta
- Pantheon
- Flywheel
Nginx is faster than Apache
New Relic
- How to know what is causing the bottleneck php + mysql?
- Application performance monitoring tool APM
- Free trial for pro version
- Profiles offer lots of good performance info
- Time broken down by php + database
- Response time by plugin and hooks.
- Slide deck shows examples for JetPack, Wordfence, Beaver Builder
How to test wp admin?
- Site district does test for wp admin
- Sometimes what makes front end slow is different from back end
- Yoast SEO can run slowly on backend
Considerations
- not number of plugin, but what they are doing
- theme can also be a major part of your performance problem
  - test early and often

Page Load Speed

Start with webpage test
Image optimization
- check score for compressed images
- how much of page content is image data
- check for large png files that could be jpg
- often can compress more even if you have an A
Analyse waterfall
Defer images, CSS and JavaScript

Summary

Measure your performance first
Good host
If TTFB is slow, profile with new relic
Image optimization

Scott Gruber