Hello AndyLai,
You will need to contact our Managed Hosting team to have that done as they do not operate out of this public forum.
Best Regards,
TJ Edens
Hello,
Thank you for your installation question. You will definitely need root access in order install the software by yourself. You may also opt to contact our Support team for installation. Memcached is listed on our Installable Software reference and does have an installation fee.
Varnish is a bit different as it may also need additional configuration so that may require the purchase of Managed Hosting time. Also, it is recommended that you have at least a VPS 3000S for that software due to the memory requirements.
Kindest Regards,
Scott M