Hello,
Sorry for the delay in answering. It’s related to the number of the requests from our users.
Yes, we use the WordPress Object Cache but the object cache is non-persistent. This means that data stored in the cache resides in memory only and only for the duration of the request. Cached data will not be stored persistently across page loads unless you install a persistent caching plugin.
https://codex.wordpress.org/Class_Reference/WP_Object_Cache
Very likely your hosting use caching plugins on the backend that’s why you had that problem.
Regards