Even IT professionals can't tell the difference between latency and bandwidth, or capacity and speed.

A simple rule of thumb is: If a single user experiences poor performance with your otherwise idle cluster of servers, then adding more servers will not help.

You can't imagine how often I have to have this conversation with developers, devops people, architects, business owners, etc...

"Let's just double the cores and see what happens."

"Let's not, it'll just double your costs and do nothing to improve things."

Also another recent conversation:

"Your network security middlebox doesn't use a proper network stack and is adding 5 milliseconds of latency to all datacentre communications."

"We can scale out by adding more instances if capacity is a concern!"

"That's... not what I said."