Increase Varnish TTL on cache

Overriding the time-to-live (ttl)
Sometimes your backend will misbehave. It might, depending on your setup, be easier to override the ttl in Varnish than to fix your somewhat cumbersome backend.

You need VCL to identify the objects you want and then you set the beresp.ttl to whatever you want:

sub vcl_fetch {
    if (req.url ~ "^/legacy_broken_cms/") {
        set beresp.ttl = 5d;
    }
}