AWS

AWS CloudFormation intrinsic functions

The abbreviation of the intrinsic functions

Fn::Sub is identical to !Sub

Fn::!GetAtt returns the value of an attribute from a resource

Value: !GetAtt 'VM.PublicDnsName' # get VM's Public dns name attribute

Ref returns the value of the specified parameter or resource

VpcId: !Ref VPC

Fn::Sub like string concatenation

TableName: !Sub "${EnvironmentType}-user" # EnvironmentType is a parameter created elsewhere in the CloudFormation template.

Limitation

Lambda

Per region

• Memory 128M to 10 GB (1MB increments)
• Max execution time 15 minutes
• Max size of environment variables 4 KB
• /tmp 512 MB
• Max currency 1000
• Max zip file 50 MB
• Uncompression file 250 MB

DynamoDB

• Maximum size of an item is 400 KB

API Gateway

• Default cache TTL is 300 seconds. Max is 3600 seconds