This page will contain a list of important terms and concepts related to performance and reliability engineering with links for further reading.
Ability of a system to cope with change.
In computer networking, is the ability to provide and maintain an acceptable level of service in the face of faults and challenges to normal operation.
An algorithm, design, networking protocol, program, or other system is said to scale if it is suitably efficient and practical when applied to large situations.
Read more @ https://en.wikipedia.org/wiki/Scalability
HORIZONTAL AND VERTICAL SCALING
To scale vertically (or scale up/down) means to add resources to (or remove resources from) a single node in a system, typically involving the addition of CPUs or memory to a single computer.
To scale horizontally (or scale out/in) means to add more nodes to (or remove nodes from) a system, such as adding a new computer to a distributed software application.