>I need it because it to be placed on marine vessels working on a 2mb VSAT connection not an office with a adsl or fibre connection.
Hi @Neil_mack. I do agree with the others, however I have worked with shipping vessels before, and I appreciate there are unique challenges in these environments you just don't face on land.
While the MX84 caching feature would help, it's not going to give you the performance improvement you would like. This is because (as you have correctly noted) most sites use https these days.
If it was me personally, I would deploy a Squid proxy server running on Ubuntu. The entire solution is free and rock solid. You can probably also run Squid on a Windows machine. This is on the assumption that you have a virtual server infrastructure on your vessel (you could potentially run this on a Raspberry Pi ...). I would also run a caching DNS server on this box as well.
http://www.squid-cache.org/
The biggest hassel with proxy servers is that you need to manually configure all your clients to use it. You can use a more advanced WPAD configuration to automate this process - and this is what I usually do.
https://en.wikipedia.org/wiki/Web_Proxy_Auto-Discovery_Protocol
My thoughts are if you did deploy Squid you wont need a stop watch to see the difference, it will be very noticable after it has been used for a little bit (it needs to "warm" up and get a cache of frequently used content).
Another option I can give you to think about is if you already have Cisco ISR routers on board (such as ISR 4000's). You can then buy a feature called Akamai Connect. Akamai is a super larger content delivery network. What "Akamai Connect" does is make your router a local cache node. You can get an overview of this feature here:
https://www.cisco.com/c/en/us/solutions/enterprise-networks/intelligent-wan-akamai/index.html
Example customers of Akamai include Microsoft and Apple.