The most common case I can think of is when you have local caches and randomly distribute traffic amongst your servers. The hit rate on the cache improves as you reduce the number of machines. If the cache expires before the same machine is hit again, you get no benefit from the cache at all. Even in the case where you are hitting the cache you are doing more original requests as you add more servers.

It could mean

* one of your servers is unhealthy, remove it from the pool.

* reject some requests to make the rest faster.

Removing capacity probably doesn't include removing capacity at all levels of the stack - perhaps it only means reducing the number of frontends, not db servers. That'd reduce load on the db server, allowing it to serve faster.