Since Plesk Onyx you will be able to install memcache as a Docker container and configure http(s) proxy rule for it to map to your web app.
Docker and proxy rules are available in Plesk Onyx Preview already, you can try it here https://talk.plesk.com/threads/plesk-onyx-preview-and-feedback.337172/
Yes for Memcache(d) of Plesk
Thank you for your input! We are planning to implement this functionality in upcoming releases. The request is registered as: PPM-2517
Everyone, please continue voting for this feature if you consider it important.
— ESmackloug commented
+1 I say Yes !