Unfortunately the load-balancer is not a magic-bullet curing every issue a system has. A load-balancer can be configured to do lots of things, like for example:

* limit the number of concurrent requests, and drop the others;

* limit the number of concurrent requests, but queue the others (with a timeout);

* distribute all requests uniformly (randomly or in round-robin fashion) to all backends;

* (any combination of the above);

However if the "customer" asks you to not drop or queue requests, then there is nothing the load-balancer can actually do...