Measurement of web page performance is critical when you need to track improvements and justify performance optimization budgets. Over the years, multitude of metrics were developed, from Time To First Byte and Page Load Time all the way to more modern and sophisticated metrics like Time to First Paint, ATF and Speed Index. Web browsers also added multiple APIs to allow more visibility into the stack with Navigation Timing, Resource Timing as well as User Timing APIs. The challenge with performance metrics is that they are all proxies for user experience and don’t necessarily translate directly into user satisfaction and business gains. Sergey Chernyshev reviews the reasons why we need to track performance and will introduce a new method for improving existing performance metrics using Heat Maps generated based on business requirements. Given at DevOpsQA NJ meetup: http://www.meetup.com/DevOpsQA/events/234356901/

1. U S I N G
H E AT M A P S
T O D E F I N E
P E R F O R M A N C E
M E T R I C S
S E R G E Y C H E R N Y S H E V

2. S C A L A B I L I T Y & P E R F O R M A N C E
number of users
timetoload

3. number of users
timetoload
S C A L A B I L I T Y & P E R F O R M A N C E

4. S C A L A B I L I T Y & P E R F O R M A N C E
One User
timetoload

5. W H Y D O W E M E A S U R E S P E E D ?
• Monitor for degradations (Ops)
• Analyze code for perf issues (Devs)
• Verify improvements (Devs)
• Prioritize improvements (Business)
• Budget for WPO initiatives (Business)

6. S TAT S
• Google: +500ms => -25% searches (2006)
• Amazon: +100ms => -1% revenue (2008)
• Netflix: +GZip => -43% Traffic cost (2008)
• Shopzilla: -5s => +12% Conversion rate (2009)
• Google: +400ms => -0.21% searches after experiment! (2009)
• Mozilla: -2.2s => +15.4% Downloads (2010)
• Edmunds: -77% load time => +20% page views (2011)
• DoubleClick: -1 redirect => +12% CTR (2011)
• Etsy: +160Kb => +12% bounce rate (2014)
• Trainline: -0.3s => +$11.5M / year revenue (2016)
WPOStats.com

7. R E A L U S E R M E A S U R E M E N T
• Real users (a lot of them)
• A lot of data (need to store it)
• All noise you can get, requires filtering
• Metrics are distributions
• Can correlate to business KPIs

8. S Y N T H E T I C T E S T I N G &
A N A LY S I S
• From particular location
• Tester controls instrumentation
• One metric value
• Data can have lots of details for analysis

9. T O D AY ' S M E T R I C S
• DNS, SSL/TLS, Time To First Byte (TTFB)
• Page Load, Document Complete, Fully Loaded
• First Paint
• Above the Fold Time (AFT)
• SpeedIndex

10. T I M E T O F I R S T PA I N T
• Shows when completely useless part is over
TTFP
3.5s

11. A F T ( A B O V E T H E F O L D T I M E )
• When everything is finally visible
AFT
15.3s

12. S P E E D I N D E X
• Unifies rendering progress in one number
Speed Index
8618

13. U S E R T I M I N G A P I
• Records custom JS timings on the page
• Recorded by both RUM and Synthetic tools
• Can be hard to match with user's reality
• Requires JavaScript instrumentation

14. M E A S U R E U S E R E X P E R I E N C E
• Great experience for users
• "Fast" is just a component
• Correlate what you measure
to business KPIs
• Do not measure what's easy,
measure what matters
N O T T E C H N O L O G Y

15. H E AT
M A P S
D I S C O V E R A N D
D E F I N E
W H AT M AT T E R S
U S I N G

16. U S E R A C T I O N H E AT M A P S
• Eye tracking
• Click tracking
• Hard to capture
• Shows current state
• Can be automated

17. P R O D U C T F E AT U R E H E AT M A P S
• Hard to automate
• Each industry is different
• Usually multiple templates
that power many pages
• Business team already
knows the answers

18. I N T E R A C T I O N O N T H E W E B
1. Verify destination
2. Provide primary content
3. Allow interaction
4. Show secondary content
5. Invisible tasks
6. Acknowledge action

19. D E S I G N C O M P O N E N T S
1. Verify destination
2. Primary content
…

20. H E AT M A P C U T- O U T S
Core Branding & Main Navigation Primary content

21. C O R E B R A N D I N G H E AT M A P

22. C O R E B R A N D I N G H E AT M A P

23. P R I M A RY C O N T E N T H E AT M A P

24. P R I M A RY C O N T E N T H E AT M A P

25. 11s
P R I M A RY C O N T E N T H E AT M A P
11s
Primary Content
3.5s
15.3s

26. E X T E N D E D M E T R I C S
• Time To First Paint (TTFP) - 3.5s
• Core Branding & Main Navigation - 8s
• Primary content - 11s
• ...
• Above The Fold (AFT) - 15.3s

27. S E L E C T O R - B A S E D I M P L E M E N TAT I O N
• Uses CSS selectors to define active zones
• Executes "custom metric" function in WebPageTest to
get cutout coordinates
• Downloads test results and video frames using WPT API
• Manipulates video frames and feeds into
visualmetrics.py and uses 99% threshold to grab times
• Kudos to Patrick Meenan for awesome tools

28. T H A N K Y O U !
sergey.chernyshev@gmail.com
@SergeyChe