Explanation: In Amazon ElastiCache, the number of cache nodes in the cluster is a key factor in the availability of your cluster running Memcached. The failure of a single cache node can have an impact on the availability of your application and the load on your back-end database while ElastiCache provisions a replacement for the failed cache node and it get repopulated. You can reduce this potential availability impact by spreading your memory and compute capacity over a larger number of cache nodes, each with smaller capacity, rather than using a fewer number of high capacity nodes.
Reference:
http://docs.aws.amazon.com/AmazonElastiCache/latest/UserGuide/Cache…

Explanation: The Amazon Virtual Private Cloud (Amazon VPC) allows the user to define a virtual networking environment in a private, isolated section of the Amazon Web Services (AWS) cloud. The user has complete control over the virtual networking environment. Within this virtual private cloud, the user can launch AWS resources, such as an ELB, and EC2 instances. There are two ELBs available with VPC: internet facing and internal (private) ELB.
For internal servers, such as App servers the organization can create an internal load balancer in their VPC and then place back-end application instances behind the internal load balancer. The internal load balancer will route requests to the back-end application instances, which are also using private IP addresses and only accept requests from the internal load balancer. The Internal ELB supports only one subnet in each AZ and asks the user to select a subnet while configuring internal ELB.
Reference:
http://docs.aws.amazon.com/ElasticLoadBalancing/latest/DeveloperGui…

Explanation: Amazon Resource Name (ARN) condition operators let you construct Condition elements that restrict access based on comparing a key to an ARN. ArnLike, for instance, is a case-insensitive matching of the ARN. Each of the six colon-delimited components of the ARN is checked separately and each can include a multi-character match wildcard (*) or a single-character match wildcard (?).
Reference:
http://docs.aws.amazon.com/IAM/latest/UserGuide/AccessPolicyLanguag…

Explanation: A user authenticating with Amazon Cognito will go through a multi-step process to bootstrap their credentials. Amazon Cognito has two different flows for authentication with public providers: enhanced and basic.
Reference:
http://docs.aws.amazon.com/cognito/devguide/identity/concepts/authe…

Explanation: RDS DB instance storage comes in two types: standard and provisioned IOPS. Standard storage is allocated on the Amazon EBS volumes and connected to the user’s DB instance. Provisioned IOPS uses optimized EBS volumes and an optimized configuration stack. It provides additional, dedicated capacity for the EBS I/O.
Reference:
http://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/Welcome.html

Explanation: Generally, AWS EC2 allows running 20 on-demand instances and 100 spot instances at a time. This limit can be increased by requesting at https://aws.amazon.com/contact-us/ec2-request. Excluding certain types of instances, the limit is lower than mentioned above. For g2.2xlarge, the user can run only 5 on-demand instance at a time.
Reference:
http://docs.aws.amazon.com/general/latest/gr/aws_service_limits.htm…

Explanation: While implementing the policy keys in Amazon RDS, if you use aws: SourceIp and the request comes from an Amazon EC2 instance, the instance’s public IP address is evaluated to determine if access is allowed.
Reference:
http://docs.aws.amazon.com/directconnect/latest/UserGuide/using_iam…

Explanation: In the context of AWS support, the Business and Enterprise support plans allow an unlimited number of users to open
technical support cases (supported by AWS Identity and Access Management (IAM)).
Reference:
https://aws.amazon.com/premiumsupport/faqs/

Explanation: If you need to host multiple websites (with different IPs) on a single EC2 instance, the following is the suggested method from AWS. Launch a VPC instance with two network interfaces. Assign elastic IPs from VPC EIP pool to those interfaces (Because, when the user has attached more than one network interface with an instance, AWS cannot assign public IPs to them.) Assign separate Security Groups if separate Security Groups are needed This scenario also helps for operating network appliances, such as firewalls or load balancers that have multiple private IP addresses for each network interface.
Reference:
http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/MultipleIP.html

Explanation: In Amazon IAM, the maximum length for a role name is 64 characters.
Reference:
http://docs.aws.amazon.com/IAM/latest/UserGuide/LimitationsOnEntiti…