sub vcl_recv {
  if (!client.ip ~ othervarnish) {
    set req.backend = varnish;
  }
}

sub vcl_fetch {
  if (beresp.http.X-Meta-Has-Esi && !client.ip ~ othervarnish) {
    esi;
  }
}

Request ---> VarnishA MISS --> VarnishB MISS --> Backend (success with esi parsed)

New Request ---> VarnishA HIT (success with esi parsed)
New Request ---> VarnishB HIT (fail, esi will not be parsed)