scaling

[Scaling Vertically]

- An increase in the specifications of an individual resource.
	 - upgrading a server with a larger hard drive or a faster CPU.

On Amazon EC2, this can easily be achieved by stopping an instance and resizing it to an instance type that has more RAM, CPU, IO, or networking capabilities.


[Scaling Horizontally]

- An increase in the number of resources.
	- adding more hard drives to a storage array or adding more servers to support an application.

[Stateless Applications]

- is an application that needs no knowledge of previous interactions and stores no session information.

A stateless application can scale horizontally since any request can be serviced by any of the available compute resources.


- Distribute load to multiple nodes
 	- Push model.
 		- Elastic Load Balancing (ELB).
 		- Route 53.

 	- Pull model.
 		- Amazon Simple Queue Service (SQS).
 		- Amazon Kinesis.