RDS does not support creating a DB instance - postgresql

Question

I am trying to create postgres rds using cloudformation but it give me this error
RDS does not support creating a DB instance with the following combination: DBInstanceClass=db.t2.micro, Engine=postgres, EngineVersion=13.3, LicenseModel=postgresql-license. For supported combinations of instance class and database engine version, see the documentation. (Service: AmazonRDS; Status Code: 400; Error Code: InvalidParameterCombination; Request ID: cdb3ewcd-17ef-404c-adc5-fcd04a590553; Proxy: null).
I have tried changing the instance type and EngineVersion but same error. Any help would be appreciated.
myDBEC2SecurityGroup:
Type: AWS::EC2::SecurityGroup
Properties:
GroupDescription: Frontend Access
VpcId: !Ref Ec2Vpc
SecurityGroupIngress:
- IpProtocol: tcp
FromPort: 5432
ToPort: 5432
CidrIp: 10.0.0.0/16
myDBParamGroup:
Type: AWS::RDS::DBParameterGroup
Properties:
Description: Database Parameter Group + pg_stat_statements
Family: postgres13
Parameters:
shared_preload_libraries: pg_stat_statements
myDBSubnetGroup:
Type: AWS::RDS::DBSubnetGroup
Properties:
DBSubnetGroupDescription: DB Private Subnet
SubnetIds:
- !Ref Ec2SubnetPrivate1
- !Ref Ec2SubnetPrivate2
pgDB:
Type: AWS::RDS::DBInstance
Properties:
DBName: !Ref 'DBName'
AllocatedStorage: !Ref DBAllocatedStorage
DBInstanceClass: !Ref 'DBInstanceClass'
Engine: postgres
EngineVersion: '13.3'
MasterUsername: !Ref 'DBUser'
MasterUserPassword: !Ref 'DBPassword'
MultiAZ: !Ref 'MultiAZ'
Tags:
- Key: Name
Value: Master Database
DBSubnetGroupName: !Ref myDBSubnetGroup
DBParameterGroupName: !Ref myDBParamGroup
VPCSecurityGroups:
- Fn::GetAtt:
- myDBEC2SecurityGroup
- GroupId

Answer 1

You have to find the instance that supports your engine postgres and version 13.3 for your region. To do this you should use the following command:
aws rds describe-orderable-db-instance-options --engine postgres --engine-version 13.3 --query "*[].{DBInstanceClass:DBInstanceClass,StorageType:StorageType}|[?StorageType=='gp2']|[].{DBInstanceClass:DBInstanceClass}" --output text
which gives (t2 is not supported at all):
db.m5.12xlarge
db.m5.16xlarge
db.m5.24xlarge
db.m5.2xlarge
db.m5.4xlarge
db.m5.8xlarge
db.m5.large
db.m5.xlarge
db.m6g.12xlarge
db.m6g.16xlarge
db.m6g.2xlarge
db.m6g.4xlarge
db.m6g.8xlarge
db.m6g.large
db.m6g.xlarge
db.r5.12xlarge
db.r5.16xlarge
db.r5.24xlarge
db.r5.2xlarge
db.r5.4xlarge
db.r5.8xlarge
db.r5b.12xlarge
db.r5b.16xlarge
db.r5b.24xlarge
db.r5b.2xlarge
db.r5b.4xlarge
db.r5b.8xlarge
db.r5b.large
db.r5b.xlarge
db.r5.large
db.r5.xlarge
db.r6g.12xlarge
db.r6g.16xlarge
db.r6g.2xlarge
db.r6g.4xlarge
db.r6g.8xlarge
db.r6g.large
db.r6g.xlarge
db.t3.2xlarge
db.t3.large
db.t3.medium
db.t3.micro
db.t3.small
db.t3.xlarge
db.t4g.2xlarge
db.t4g.large
db.t4g.medium
db.t4g.micro
db.t4g.small
db.t4g.xlarge
db.x2g.12xlarge
db.x2g.16xlarge
db.x2g.2xlarge
db.x2g.4xlarge
db.x2g.8xlarge
db.x2g.large
db.x2g.xlarge