Event Processing

• SQS: Lambda will poll the message from SQS, if failed to processing, will do retry, after max of times, will send to DLQ
• SNS: If failed, do retry on Lambda side, after max of times send to DLQ

Caching

• Static content will be cached by using CloudFront
• Dynamic content can also be cache at CloudFront, use TTL to control the cache; closest to the user location
• API Gateway, is regional service, can do caching as well
• Can use Redis, DAX for DB caching

Blocking IP Address in AWS

• You can use NACL on VPC level to block IP addresses
• ALB has Security Group and has connection Termintaion
• EC2 can stay in private subnet

• NLB doesn't have Security Group
• EC2 will see Client'IP address

• CloudFront, can use Geo location to block one country Ip addresses to access
• Use extra service WAF, to do more advanced IP address filtering
• NACL is not helpful anymore, because ALB' security group allows all CloudFront IP addresses, not client IP address

High Performance Computing (HPC)

• For a destributed EC2 system (EC2 instances need to talk to each others), use a Clouster Placement Group for good network perofrmance

• EC2 Enhanced Netowrking for better Compute and networking
• Use Elastic Netowrk Adapter (ENA)
• Elastic Fabric Adapter (EFA), only for Linux

EC2 Instance High Availability

• How to failover to a Standby EC2 instances?
• We can create a CloudWatch alarm based on CPU for example
• then trigger a Lambda
  • Start the instance
  • Attach the Elastic IP to Standby
  • Deattach the Elastic IP from old instances
  • EIP can only attach one instance

• You have 2 AZ
• ASG Setting with 1min, 1max, 1 desired
• Use EIP
• When EC2 in AZ1 fail

• ASG will create another instance in AZ2
• Attach EIP to new instances

• If EC2 in AZ1 failed
• ASG will terminate the instance
• We can use ASG Terminate lifecycle hook to create a EBS Snapshot to S3
• Then ASG will create another EC2 instance in AZ2
• Use ASG Launch lifecycle hook to attach EBS snapshot to the new instances

• Have to use NLB because SSH is Layer 4
• Each AZ can have one NLB talk to Bastion Host

EFA is an Ehanced ENA. for linux