What is the difference between High Availability and Scalability?

High Availability (High Availability) and scalability (Scalability) are two different aspects related to ensuring efficient and reliable operation of systems in IT, but they have different goals:

HA - responsible for ensuring the system's sustainability and providing services to users even in the event of failures or errors. The main goal is to ensure that the system is always accessible and provides services smoothly. HA includes measures that allow the system to continue operating even if a failure or problem occurs, ensuring a high level of reliability.

Aimed at the system's ability to respond effectively to various types of growth (for example, traffic). Scalability includes the ability of a system to expand or decrease to provide optimal performance under variable conditions.

These concepts may seem similar and even interact, they are distinguished mainly by their goals. HA focuses on reliability and avoiding interruptions, while scalability aims at the ability to adapt to changes in system sizes or volumes to ensure efficient functioning (avoiding interruptions also comes here; this is where High Availability and Scalability intersect).