What is the difference between scalability and elasticity?

Question

I\'ve heard many people using both terms interchangeably. However, in my opinion there is difference between them:

SCALABILITY - ability of a softwa

Answer 1

Usually, when someone says a platform or architectural scales, they mean that hardware costs increase linearly with demand. For example, if one server can handle 50 users, 2 servers can handle 100 users and 10 servers can handle 500 users. If every 1,000 users you get, you need 2x the amount of servers, then it can be said your design does not scale, as you would quickly run out of money as your user count grew.

Elasticity is used to describe how well your architecture can adapt to workload in real time. For example, if you had one user logon every hour to your site, then you'd really only need one server to handle this. However, if all of a sudden, 50,000 users all logged on at once, can your architecture quickly (and possibly automatically) provision new web servers on the fly to handle this load? If so, it could be said that your design is elastic.