CPSC 4820 - DAY 3
JANUARY 23, 2018

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AMAZON S3 Provides read-after-write consistency for PUTS of new objects in
your s3 bucket in all regions with one caveat.  The caveat is that if you make
a HEAD or GET request to the key name (to find if the object exists) before
creating the object, Amazon s3 provides eventual consistency for 
read-after-write.

Amazon s3 offers eventual consistency for overwrite PUTS and DELETES in all 
regions.

Consistent vs. Eventually consistent - eventually they will have the same
answer.  Depends on race condition.  S3 makes only promise of eventual
consistency in an overwrite.

Amazon VPC - an isolated, private virtual network on the AWS cloud.

Subnet - defines a range of IP addresses in your VPC.

You can launch AWS resources into a subnet you select.

A private subnet should be used for resources that won't be accessible over the
internet.

A public subnet should be used for resources that will be accessed over the
internet.

Each subnet must reside entirely within one Availability Zone

Security group - like a firewall.

Network access control lists (ACLs) - security at the subnet level.