CaaS-related performance Lighthouse score drop in Milo?

[Axelcureno]

I came to know by word of @auniverseaway that a page in Milo that uses CaaS can see a Lighthouse score being dropped by at least 20%? I'd like to start the conversation to better understand the root cause and perhaps work on a possible fix to improve the score.

[chrischrischris]

The CaaS collection is pretty heavy in size (125k) and js (700ms execution time). Some of that can only be addressed by the CaaS team but looking at pagespeed there are definitely some things that can be done. A few things that stood out:

• Some card images are way too big. The Xfinity Creative photo is 900k! Need to talk to authors to fix.
• Marquee image lazy loaded
  • The loadLCPImage function is only removing lazy from one of the marqee images, this could be fixed to eagerly load all marquee images if that's at the top of the page.
• The CaaS collection on the main customer-stories page is not lazy loaded. Since it's above-the-fold there should be a slight perf gain from loading directly
  • To disable lazy loading, no-lazy needs to be added to the text content of the CaaS link. You could try copying the page and seeing if it makes a difference.

It's worth taking a look at https://pagespeed.web.dev/report?url=https%3A%2F%2Fbusiness.adobe.com%2Fcustomer-success-stories and going through all the details. You'll see that a lot of the reported issues are in the dexter caas code or in martech.