You can install Memcached via addin.

cd /usr/local/apnscp/resources/playbooks
git clone https://github.com/thundersquared/apiscp-memcached.git addins/apiscp-memcached
ansible-playbook addin.yml --extra-vars=addin=apiscp-memcached

You should then (re)build your PECL packages. Learn how here

To start using your freshly installed memcached:

memcached -l 127.0.0.1 -p 40010 -m 128

Do not run memcached without binding locally or to a unix-domain socket (-s /path/to/socket). See also Memcached DDoS explained.