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AWS SAA > HA and Scaling > Flashcards

HA and Scaling Flashcards

1
Q

What are the 3 Ws for scaling?

A

What, Where, When

What resources, Where in the OSI model, When to scale

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2
Q

What is a launch template?

A

A launch template specifies all the configs needed to build an ec2 instance

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3
Q

*What goes into a launch template?

A

AMI, instance size, SG, possibly network information (VPC), User data

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4
Q

What happens if you include networking (e.g. VPC) information in a launch template?

A

The template can’t be used with Auto Scaling Groups as the ASG has to specify the VPC

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5
Q

Between Launch Templates and Launch Configurations what should you use?

A

Use Launch Templates as they are newer

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6
Q

How do you change user data when there is a launch template?

A

You will need to create a new version of the launch template, and include the adjusted user data in it.

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7
Q

What is the difference between launch templates and configurations for mutability, networking, autoscaling, configs?

A
  1. Versioned vs. immutable
  2. Optional to include vs. can’t include
  3. For more than Autoscaling vs. only for autoscaling
  4. more config granularity options vs. less options
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8
Q

What is an AutoScaling Group?

A

Collection of instances treated as a single unit and defines where to create/destroy instances

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9
Q

What feature should you use if you want an ELB with AutoScaling Group?

A

You need to set the ASG to use the health checks of the LB so that the ASG will deregister and spin up instances at the LB level

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10
Q

What networking does an ASG define? What should you do for HA?

A

ASG needs to define the VPC and AZ, of which a minimum of 2 different AZ’s should be used

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11
Q

What is the minimum # autoscaling you should usually go?

A

2 is the lowest you usually should go

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12
Q

Can you mix instance types? Which ones? Why?

A

Yes, On-demand and spot instances, RI, use spot instances to save money

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13
Q

What 3 attributes doe group size policy contain?

A

Min, Max, Desired

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14
Q

What do you want to do for scaling in and scaling out? What are you preventing?

A

Scale in conservatively (fast to terminate, slowly roll back), scale out aggressively (warm up period, handle workload). Prevent Thrashing

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15
Q

What is warm-up period? Why?

A

Instances are not placed behind a LB, and not included in the health check to prevent being terminated while being spun up.

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16
Q

What is cool-down period? Why? Default?

A

Applies to both creation/termination, ignores multiple scaling events within a time period. Prevents runaway scaling. Default time period is 5 minutes

17
Q

What are the 3 types of scaling?

A
  1. Reactive
  2. Scheduled
  3. Predictive
18
Q

What is Reactive Scaling?

A

Measure the data points and catchup to create/terminate resources

19
Q

What is Scheduled Scaling?

A

When you have a predictable workload, you can schedule resources to come up before needed

20
Q

What is Predictive Scaling?

A

AWS service using ML to predict when to scale

21
Q

What do you need to do if you need an instance that there can only be one copy but it needs to be HA?

A

You should configure a steady state auto scaling group with min, max, desired set to 1

22
Q

How do you save money mixing instance types?

A

Use RI to cover min counts, and Spot instances to scale

23
Q

How do you save money mixing instance types?

A

Use RI to cover min counts, and Spot instances to scale

24
Q

What are the 4 ways to scale RDS?

A
  1. Vertical scaling
  2. Scale Storage space
  3. Use Read Replicas
  4. Use Aurora Serverless
25
Q

What do you need to watch out for when scaling RDS Storage?

A

Storage can be scaled up but not down.

26
Q

What increments does Aurora scale storage?

A

10 GB increments automatically

27
Q

For RDS Read Replicas is the endpoint the same or different than the writer? What about cross region?

A

Read endpoints are separate from the writer. You can have a cross region read replica.

28
Q

What option should you pick if it is viable to switch db engines?

A

You should pick DynamoDB and refactor over scaling RDS

29
Q

What are the 2 scaling options for DyanmoDB?

A
  1. Provisioned

2. On-Demand

30
Q

What is Provisioned Scaling for DynamoDB?

A

For Predictable workloads, more cost effective, you set the read/write capacity and target utilization

31
Q

What is On-Demand for DynamoDB?

A

For sporadic workloads, less cost effective, pay per read/write

32
Q

What limit is there on switching between provisioned and on-demand DynamoDB models?

A

A 24 hour switch limit

33
Q

What should be avoided for DynamoDB performance?

A

Hot Keys

34
Q

What services do AutoScaling Groups work for?

A

Only EC2

35
Q

How do you speed up provisioning instances in AutoScaling Groups?

A

You should bake the AMI’s over using User Data

AWS SAA (20 decks)

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