Hallway Hangout: Performance End of Year Review 2023

Cost Analysis

@pbearne highlighted that there’s no tie back to numbers, costs etc in the presentation from @flixos90 — cost of search engines crawling the save in value, cost saving of hosting companies etc — wondered if there’s a way we can obtain any dollar values against what these performance improvements actually mean. @flixos90 advised that we can try to draw general conclusions but mostly to get real numbers is do individual case studies, maybe there are hosting providers that are happy to share how much LCP improved and what this means for revenue / cost, specific case studies would be the way forward here, it would be difficult to establish this more widely. Maybe there’s a call we can put out to ask any hosting providers if they’re willing to do a case study

TTFB Improvements

@joemcgill went on to discuss the second to last slide, idea that we can get more benefit from focusing on FE LCP improvements, the underlying TTFB improvements — this was Joe’s initial gut instinct, websites that care about performance fix TTFB by not hitting WP application at all, using aggressive page caching etc. However, mindful at the fact that WP 6.3 we had 2 big opportunities that had a big impact on client slide: removal of emoji loading script and image loading improvements (the addition of fetchpriority and the lazy loading improvements). Whilst focusing on FE LCP improvements are easier, do we have opportunities of similar scale that would make sense, or are we just driving server side?

@flixos90 added that the difference is that most of client side improvements that we have done are larger efforts, whereas improving server side cut off milliseconds that add up over time. There may be a point where we have no idea what to improve on the client side, but there are a few things mentioned on image sizes attribute is one of them, optimizing how large images are loaded, continuing to optimize fetchpriority and lazy loading are applied, will drive up the passing rate more. Felix added, the main indicator is when we look at mobile, this is where the big difference is happening, when you look at LCP and TTFB together, but LCP in 6.3 was a lot more (probably came from client side improvements predominantly). Desktop TTFB was more visible than mobile. We always benchmark on a desktop machine, so mobile devices are lower powered. Maybe it’s just because for mobile specifically TTFB improvements have a lower role, and it’s more about the device configuration.

@joemcgill went on to ask whether we’re just looking at the % that are getting good scores, rather than the value of TTFB or change in TTFB metric. Could we have made the same amount of improvement as desktop, but not a big enough value to go over the threshold of the passing rate. Felix mentioned he has looked at these numbers as he has assumed the same thing. When you look at aggregated data, there weren’t major improvements in similar ways. Overall scale is still not visible. 

2024 Suggestions

@pbearne suggested images, do the amounts of images in the media library impact going through file numbers, orphan image sizes left around — should we have a tool to help clean this up? Some images are left behind from changing themes etc, does this bloat the number of images in the file system? If it does, would a simple tool help remove images that are not current. Here, @adamsilverstein suggested that some regenerate thumbnails plugins, URLs still point to old images if they’re removed. Thinks everyone has things in folders, if people have them in one giant directory it would impact. File loading may not be an image, but one place to look at was maybe the attachments in posts database, when doing lookups etc, maybe there are places we can eliminate here — but suspect this is a small improvement. The remaining images are mostly about storage space wasted and incurring costs. For performance on end users, doubt this has a notable impact.

@pbearne also added that the interactivity API would be a great place to investigate. @flixos90 added we should think for next year what can we do to improve interactivity, facilitate WP sites having more responsive interactions. The new metrics means this is more significant. Load time performance, but split this more to cover interactivity. The team discussed any other intentional research what leads to lower INP passing rate, hypotheses have been created but could do with having confidence in knowing where the problems lie. More research is definitely needed.

@flixos90 continued, what do the TTFB numbers mean for us? This year we have been focused on improving TTFB in core, but thinking about mobile representation, are there other ways we should try to move forward TTFB — what about enhancing APIs to provide more guardrails to plugins, there are a lot of other components to this, could argue that small changes don’t cover lower powered — something core can do better to facilitate caching for more people. Can we unlock caching for sites that have hosts that don’t provide this feature etc. @joemcgill added that we had talked about trying to use the SQLite Database as an object cache for sites that don’t have a better option — could we think on this again?

@flixos90 liked this idea, worth exploring — this would be for object caching, could we use it for page caching? Persistent object cache avoids using database requests, not that significant for overall performance. Full page caching would be more beneficial to focus on. Avoiding hitting application altogether could be better. Was looking at full page caching in the CWV dashboard, surprised that the popular caching plugins their TTFB scores are not beating the general WP TTFB numbers, seems counter intuitive. Could we dive into this more? Were these plugins specific to having the full page caching, could not be turned on. @adamsilverstein added that we can get a geographical bias, if the plugin is popular in a region with slower internet, it’s not their problem its the users. @adamsilverstein highlighted that you can breakdown on the settings page of the CWV report by geographical region. Could query this in HTTPHTTP HTTP is an acronym for Hyper Text Transfer Protocol. HTTP is the underlying protocol used by the World Wide Web and this protocol defines how messages are formatted and transmitted, and what actions Web servers and browsers should take in response to various commands. Archive to see if there are patterns. Other considerations are all WP plugins that offer full page caching offer this at the application level, not as good as having the layer at the hosting level.

Concluding Statements

@pbearne raised that as a plugin developer, having good tests or validations that I’m doing it right, i.e. plugin checker, improving this and helping you recognise where improvements should be made, is something that can improve overall performance. More work in this field would benefit overall, especially if we can do themes as well.

@joemcgill concluded that the team are thankful to Felix for pulling these numbers together, easy to not be able to see the big picture. But really great to see the impact the performance team has made is great to see!