APCu is a user-accessible PHP cache. Pantheon provides APCu by default across all plans, but the size of the APCu memory cache (apc.shm_size) varies depending on the service level. See the Application Containers overview to learn more about APCu on Pantheon's container architecture.
Yes, APCu can be used as a cache backend or a "key-value store"; however, this is not recommended. APCu lacks the ability to span multiple application containers. Instead, Pantheon provides a Redis-based Object Cache as a caching backend for Drupal and WordPress, which has coherence across multiple application containers.
shm_size in phpinfo.
As this is not a runtime configuration, the
shm_size cannot be changed. If a greater
shm_size is needed, then the two options available are to optimize the codebase to operate within the service level, or to upgrade the site account for a larger
No. The Clear Caches button in the Site Dashboard does not interact with APCu. The function
apcu_clear_cache will clear the APCu cache for a single application container.