i read though the documentation for API's to create new instances. not sure if it allows Geographical Horizontal cloning, rather i wanted to clone same droplet in a different geographical region for better Content delivery .

do you know any tutorial which you used varnish installation with wordpress? i am new at programming and server , i found a program called easy engine and he didnt not recommend varnish its from rtcamp you can check it . ?

THe other major problem with do is lack of storage space which is going to force me to use google cloud storage or s3 , that said i might try cloud front for a year with free quota .

do you know any good tutorials for varnish with wordpress and nginx etc ?
do you know any tutorails for using external storage with do ?
let me know thank you

How much data are you expecting to storage on your server? because big data means big costs transferring/replicating this data to different regions, that's why a caching system could work better, the "problem" with caching is you need to create your app around caching, that means no cookies or sessions, except where you really need them, and in that case you create rules on your cache system to avoid caching such sections of your site ie: you login/profile/setting/shoppingcart/etc sections, everything else should be cached and you need to avoid cookies and sessions there.

Again Cloudflare is free (has premium but not needed on most cases) is hassle free and as a CDN offers cached copies of your data from the nearest geographical zone to your users READ MORE: Cloudflare , also works as your DNS/NS server which is great, gives you free SSL, caching, security against attacks, and more.

Also if you have that many data you need to storage in a service like S3 (which only accepts static content ie: images, txt, css, js, etc) you probably don't need to store much in your server, so no need to replicate your server and again a caching system will be better. And you can use Cloudflare CDN to cache and deliver your content (even from Amazon S3/Google) from nearest geo zone to your users.

So here is What I would do if your site is not too complex to require different:

Create your server on DO (lets called origin) and setup what you need like nginx, php, mean, whatever you are using.

Create a free account at Cloudflare and host your application domain there, and create record directing visitors to your DO server (Origin). Optionally you can create an extra cheap server and install varnish on it, you can do this to avoid high traffic to your Origin server in case you have too many visitors.

If you do the last you configure your domain at Cloudflare this way:

Example:
A record: www --> Varnish (IP address) --> Origin IP address

So Varnish caches your content from Origin server and Cloudflare distribuits your content Globally.

If you choose to also use S3/Google you can create a subdomain for your static content at cloudflare too, ie:
CNAME record: cdn.yourdomain.com --> Amazon S3/Google Storage, so again Cloudflare will cache and distribute your content globally from Amazon/Google.

Now there are plenty guides for Varnish (choose Varnish version 4) all over the web and DO community, in CentOS is pretty easy as to add repos from Varnish.org, yum install varnish, edit /etc/sysconfig/varnish to choose how much storage and storage type you want to use (RAM/HDD) and then edit /etc/varnish/default.vcl to setup your backend. Also this is the file where you will add rules as you needed. There is plenty documentation on varnish.org too.

Here are some tips you will need with Wordpress and Varnish/Cloudflare

Create/look for rules to avoid caching /wp-admin /wp-login.php

On Varnish is like this:

sub vcl_recv {
    if (req.url ~ "((wp-(login|admin|comments-post.php|cron.php))|login)" || req.url ~ "preview=true" || req.url ~ "xmlrpc.php") {
        return (pass);
    } else {
        unset req.http.cookie;
    }
}

sub vcl_backend_response {
    # Dont cache admin

    if (bereq.url ~ "(wp-(login|admin|comments-post.php|cron.php))|login" || bereq.url ~ "preview=true" || bereq.url ~ "xmlrpc.php") {
        set beresp.uncacheable = true;
        set beresp.ttl = 120s;
        return (deliver);
    } else {
        if ( beresp.ttl > 0s ) {
                unset beresp.http.set-cookie;
            }
            # Our cache TTL
            set beresp.ttl = 10s;
            set beresp.grace = 24h;
            return(deliver);
    }

On Cloudflare is a simple "Page rule" you fill on a form like this one:
domain.com/wp-admin/
Security Profile: High, Cache level: Bypass cache

Also if you use S3/Google with Wordpress you will need to be sure to call all your static content from your CDN domain like the one we setup on cloudflare before cdn.yourdomain.com, you can use WC Total Cache plugin for this.

I know it can sound challenging if you are new at this but is pretty easy and reliable once you get it. Now as a final comment all this is really necessary if you are handling high concurrence of traffic, if you have few users maybe all you need is Cloudflare and one DO main server. Good luck!