The overhead is minimal, it only happens when adding or removing hosts, even if you have thousands on backend nodes that are changing all the time it is incredibly unlikely there will ever be a measurable difference (also this only makes a real difference for additions, removals are still O(n), so if you are using a proxy with thousands of backend nodes that are added and removed multiple times per second a List is not the ideal structure anyway). The real issue though is that your approach is not thread safe, so adding or removing a host could cause incoming requests to fail with a ConcurrentModificationException if the HostSelector attempts to iterate the host. The solution to this would be to use a thread safe list, which will either incur the same copy cost (with CopyOnWriteArrayList) or add runtime overhead (if some kind of synchronized List is used) that has the potential to significantly degrade the performance of the proxy. Stuart On Fri, May 12, 2017 at 8:28 PM, anurag singhal <anurags.dreams(a)gmail.com&gt; wrote: