Traffic costs between EC2 instances, AZs, and VPCs

Often times when running on AWS you will have multiple AZs, accounts and VPCs.  This is a simple summary of EC2 data transfer costs:

1. Within the same AZ  : Free: It is within the same AZ and over private IP.
2. Between two AZs :   Cost. Will incur inter-az charges for both inbound and outbound

3. Between Accounts in different VPCs :  Cost. Inter-az charges are applicable for data transfer charges between instances in the different AZ's (same region) and in different accounts.
4. Between one EC2 classic instance and VPC EC2 instance in a same AZ : Cost
5. Instances to S3 in the same region: Free
6. Instance to S3 in different region: Cost. cross region charges

MFA made easy

AWS accounts can use a virtual MFA (iPhone, Android etc).  This allows you to secure your AWS account more then just using a simple password.  For the iPhone, the Google Authenticator application is certified with AWS MFA.  http://aws.amazon.com/mfa/