The PHP setup here at Opalstack is configured with support for Memcached, Redis, and Opcache.
Memcached is pre-installed on our servers, so you can use that exactly as you did at WebFaction.
Redis is not pre-installed on our servers, but you can install it yourself and use it exactly as you did at WebFaction.
Note that if you were using a "custom app listening on port" application at WF for memcached or redis, you can use a "proxy port" application here for the same purpose. You also have the option of using a filesystem socket in your shell user home directory.
Opcache is enabled by default for all PHP apps running on our builtin PHP setup.