DR, Scaling and High Availability Flashcards
What does the AWS Application Discovery Service do?
Provides information on you on premise sever infrastructure and dependencies
Can a launch configuration be changed after creation? Can a launch template?
A configuration cannot be changed after creation. You need to create a new one. A launch template is versioned and can be changed after creation.
Why would you use a network load balancer?
For high throughput TCP traffic. High performance millions requests/second and low latency processing (less than 100msec)
If your ELB is setup for SSL (HTTPS) termination and is directing load to EC2 instances where does decryption of the traffic occur?
On the ELB. Encryption of traffic is between the web client and the ELB, so the ELB is responsible for encryption.
Whats the default cooldown period for an auto-scaling group?
300 Seconds
What are the 3 types of load balancer’s in AWS?
Network (OSI Layer 4 only) Application Classic
What is the difference between Horizontal Scaling and High Availability?
Horizontal Scaling: Increase the number of instances(or scale them in) - performance HA: Run instances for the app over multple AZ’s
You have a client which requires a static IP for your ELB. But, you also need the functions of an application load balancer with https. What could you do?
Use a network load balancer with TCP listener and forward the traffic to an ALB. The ALB performs TLS termination and routes requests appropriately.
For traffic routed to an instance via an ALB, can the instance see the originating client IP? Why, Why not?
No, you can’t. The application will see the Private IP of the ALB. The original IP is located in the X-Fowarded-For header on the request. The ALB performs the connection termination on the inbound request and opens a new connection to the instance using the ALB’s PRIVATE IP.
Where does TLS termination occur?
On the ELB (NLB, ALB, Classic)
For traffic routed via a Network Load Balancer - can the instance see the originating request IP?
Yes
How do you limit an instance to only serve traffic from requests from an ELB?
You reference the ELB’s security group in the inbound rules for the instances security group
Is vertical scalability best suited for distributed or non distributed systems?
Non distributed - specifically think of RDMS’s
What are 3 types of scaling policies?
Simple Step Target (Scaling out to maintain a utilisation metric)
What is the default termination policy for instances in an ASG?
Kill the instance with the oldest launch configuration first in the AZ with the most instances
In AWS, Horizontal scalability is referred to as ___ ?
Elasticity
What are the 3 step adjustments in a step scaling policy
Lower Bound for the cloudwatch metric Upper Bound for the cloudwatch metric % Amount To Scale
A client needs to whitelist an IP for your load balanced AWS application. What load balancer should you use on the AWS side?
A Network Load Balancer as this has a public facing EIP