Redirect based on value of origin_host from memcache. Needs nginx-lua and nginx-memc modules.

nginx_redirect_from_memcached

server {
    listen       80;
    server_name  example.com;

    root /var/www/example.com;

    set $origin_host 'origin.example.com';

    access_log  /var/log/nginx/example.com.access.log  main;

    location / {
        access_by_lua '
            local res = ngx.location.capture("/memcached", { args = { cmd = "get", key = "origin_host" } } )
            if res.status == 200 then
                ngx.var.origin_host = res.body
            end
        ';
        header_filter_by_lua '
            ngx.status = 301
            ngx.header["Location"] = "http://" .. ngx.var.origin_host .. ngx.var.uri;
        ';
    }

    location /memcached {
        internal;

        set $memc_cmd $arg_cmd;
        set $memc_key $arg_key;
        memc_pass 127.0.0.1:11211;
        
    }
}