Correct, this would mean it could take up to 1 second for an operation to complete, given that it will wait up to 500ms to get the operation in the queue and then up to 500ms for it to complete. Before it would wait up to 10s to get a slot in the queue.

From reading the spymemcached source code, it appears opTimeout is only used when doing synchronous gets / sets. In our case we set that timeout explicitely on the asyncGet call. I'm just setting it globally here in case it happens to affect anything else I am not aware of.