Each hosting plan at Kinsta includes a certain number of PHP threads. PHP threads determine how many simultaneous requests your WordPress site can handle at a given time. To put it simply, each uncached request to your site is handled by a PHP Thread.
For example, if you are running a WooCommerce site, your checkout page is intentionally not cached (with Nginx rule or cookie) to ensure proper functionality. The uncached request is handled by a PHP thread, which goes into a queue. If you have more requests than you do PHP thread, the queue starts to reject new requests which could result in 502/504 errors or incomplete requests.
Therefore, some WordPress sites will need more PHP thread than others to ensure the best performance. Specifically, any site that has a high rate of cache BYPASS/MISS traffic and a large number of concurrent users will need relatively more PHP threads. We refer to these types of sites as being highly dynamic.
Types of sites which would be considered dynamic include:
- eCommerce: WooCommerce, Easy Digital Downloads, etc.
- Membership: MemberPress, Ultimate Membership Pro, etc.
- Learning Management System: LearnDash, Lifter LMS, etc.
- Forum: bbPress, BuddyPress, etc.
Recommendations for Sites with a Lot of Uncacheable Content
We don’t recommend running dynamic sites (eCommerce, membership, LMS, forum) on plans with 2 PHP threads (Single 35k and WP 2 plans).
These types of sites will run on a plan with 2 PHP threads, but the ability of these sites to handle concurrent users while using 2 PHP threads will be quite limited.
If you only expect light traffic, it’s fine to run these types of sites on a plan with 2 PHP threads. However, if you do opt to run a dynamic website on a plan with 2 PHP threads and experience slow performance or 502 errors, our support team will encourage you to upgrade to a plan with 4 PHP threads or more (WP 5 and higher plans).
Our support team will only provide input on debugging 502s or slow performance for dynamic sites hosted on plans with more than 2 PHP threads.
Additional Resources
- If you want to learn more about how uncached content is handled at Kinsta, check out our in-depth article on PHP threads.
- Besides PHP threads, there are other factors that can impact the performance of your eCommerce or membership site. Take a look at our do’s and don’ts for hosting WordPress membership sites.
