Scalability is the number of requests an application can handle

▪ Measured by the number of requests and it can effectively support simultaneously.

▪ If no longer handle any more simultaneous requests, it has reached its scalability limit.

▪ To prevent downtime, and reduce latency, you must scale

▪ Horizontal scaling and vertical scaling both involve adding resources to your computing infrastructure

▪ Horizontal scaling by adding more machines

▪ Vertical scaling by adding more power

https://www.section.io/blog/scaling-horizontally-vs-vertically/