To maximize your site’s performance on Pantheon and to take advantage of our Global CDN, you'll need to configure your site's performance settings.
Learn industry best practices for Drupal caching, how to take advantage of them on the platform, and troubleshooting common issues with help from the experts at Pantheon.
/admin/config/development/performance for Drupal's performance settings.
In Drupal 9, anonymous page caching is enabled by default. There is no option to turn it on or off. To disable caching for development purposes, set the "Page cache maximum age" to no caching.
Page cache maximum age sets the max-age value in the Cache-Control headers that are output by Drupal 9. The only value that will disable Drupal's caching is "no caching". For an in-depth explanation of the max-age header, see the W3.org official documentation.
Pantheon uses HTTP/2 which allows files to download in parallel. This can potentially make aggregation unnecessary for your site. Aggregation depends on several factors, including:
- File sizes
- Number of files
- End users' browsers
We recommend that you keep aggregation enabled if you aren't familiar with how aggregation factors apply to your site.
- The TCP foundations of today's HTTP/2 deployments still impose ordering overhead that undermines the intended parallelism. In real-world environments, we've seen HTTP/2 with no aggregation perform substantially worse (hundreds of milliseconds) than pages using aggregation. This overhead occurs even with HTTP/2 push, though that reduces it somewhat. QUIC may solve this gap, but it's even more experimental than Brotli. As of January 2018, it isn't clear if QUIC will find broad support and deployment.
Other modules like
views.module, which is now in Drupal 9's core, and
panels.module contain their own caching options, which are much more fine-grained than the basic Drupal cache settings. If you use these modules, you should consider implementing their cache settings to provide a good logged-in user experience.