Section - High Availability and Scaling

Question 1

What is a Launch Template?

Answer 1

• A launch template specifies all the needed settings that go into building out an EC2 instance.
• It is a collection of settings you can configure so you don’t have to walk through the EC2 wizard over and over.
• You need to know it includes the AMI, EC2 instance size, security groups amd potentially network information.
• NB: When network information is added, template cannot be used on auto-scaling.

Question 2

Launch Templates Vs. Launch Configurations?

Answer 2

Templates:

• More than just autoscaling
• Supports versioning
• More granularity
• AWS recommended

Configurations:

• Only for autoscaling
• Immutable
• Limited configurations options
• Don’t use them

Question 3

What are Auto Scaling Groups?

Answer 3

• An Auto Scaling Group contains a collection of EC2 instances that are treated as a collective group for purposes of scaling and management.
• Steps of Auto Scaling:
  
  • 1. Define your Template
  • 2. Networking and Purchasing (Multipe AZs, Instance types: spot instances/ on demand or reserved )
  • 3. ELB configuration
  • 4. Set Scaling Policies (desired capacity)
  • 5. Notifications (SNS)

Question 4

What are the Setting Capacity Limits?

Answer 4

• Minimum
  
  • This is the lowest number of EC2 instances you’ll ever have online. you won’t dip bellow this.
  • Always set a minimum of 2 instances (high availability)
• Maximum
  
  • The highest number of EC2 instances you’ll ever provision.
• Desired capacity
  
  • How many instances do you want right now. never lower than minimum and never higher than maximum.

Question 5

Exam Tips: Auto Scaling and High Availability?

Answer 5

• Auto Scaling is important for creating a high available application
• Remember to select an answer that spread resources out over multiple Availability Zones and utilize load balancers.
• Networking
  
  • Auto Scaling groups will contain the location of where your instances live.
• Always select answers that include the elastic load balancer as well as the use of the ELB health checks.

Question 6

Instance Warm-Up and Cooldown?

Answer 6

• Warm-up
  
  • Stops instances from being placed behind the load balancer, failing the health check, and being terminated.
• Cooldown
  
  • Pauses Auto Scaling for a set amount of time. Helps avoid runaway scaling events.
• Avoid Thrashing
  
  • You want to create instances quickly and spin them down slowly.

Question 7

Scaling Types?

Answer 7

• Reactive Scaling
  
  • You playing catchup, Once the load is there, you measure it and then determine if you need to create more resources.
• Scheduled Scaling
  
  • If you have a predictable workload, create a scaling event to get your resources ready to go before they’re actually needeed.
• Predictive Scaling
  
  • AWS uses it’s machine learning algorithms to determine when you’ll need to scale. They are reevaluated every 24 hours to create a forecast for the next 48 hours.

Question 8

4 Ways to Scale relation database?

Answer 8

• Vertical Scaling
  
  • Resizing the database from one size to another can create greater performance
• Scaling Storage
  
  • Storage can be resized, but it’s only able to go up, NOT DOWN.
• Read Replicas
  
  • Creating read-only copies of our data can help spread out the workload.
• Aurora Serverless
  
  • We can offload the scaling to AWS. Excels with unpredictable workloads.

Question 9

What is DynamoDB?

Answer 9

• Fully Managed AWS database
• Scaling is simplified when using DynamoDB
• Provisioned Capacity:
  
  • Use Case
    
    • Generally predictable workload
  • Effort to Use
    
    • Need to review past usage to set upper and lower slaing bounds
  • Cost
    
    • Most cost-effective model
• On-Demand Capacity:
  
  • Use Case
    
    • Sporadic workload
  • Effort to use
    
    • Simple select on-demand
  • Cost
    
    • Pay small amount of money per read and write. Less cost effective.

Question 10

Exam Tips: DynamoDB?

Answer 10

• Predictable workload: Pick provisioned capacity
• Sporadic: Pick on-demand
• Switching:
  
  • You can switch, but only once per 24 hours per table

Question 11

4 Questions to Ask in the Exam?

Answer 11

• Is it highly available (Prioritize)
• Which is appropriate for situation:
  
  • Horizontal Scaling or Vertical Scaling
• Is the scaling solution cost effective
• Would switching databases fix the problem.
• Auto Scaling is only for EC2 , no other servce cab be scaled using Auto Scaling.
• Get ahead of the workload: whenever possible, favor solutions that are predictive rather than reactive. If the work loads is predictive and starts @05:00, try to pick an earlier start time.
• Bake AMIs to reduce build times. You can avoid long provisioning times by putting everything in an AMI. This is better than using user data whenever possible.
• Spread out. Make sure your’re spreading your Auto Scalling groups over multiple Availability Zones.
• Steady State Groups allow us to create situation where the failure of a legacy codebase or resource that can’t be scaled can automatically recover from failure.
  
  • 1 Minimum
  • 1 desired
  • 1 Maximum
• Elastic load balancers are essential. Make sure to enable health checks from load balancers otherwise, instances won’t be terminated and replaced when they fail health checks.