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AWS Certified Solutions Architectn CO3 > Load Balancers / High Availability 101 > Flashcards

Load Balancers / High Availability 101 Flashcards

1
Q

At a very high level, what does a Load Balancer do?

A

Balance your incoming request load (network or otherwise) across web servers / applications

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2
Q

What are the 3 types of Load Balancers offered by AWS?

A
  • Application Load Balancers
  • Network Load Balancers
  • Classic Load Balancers
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3
Q

What does ALB stand for?

A

Application Load Balancer

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4
Q

What does NLB stand for?

A

Network Load Balancer

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5
Q

What does an Application Load Balancer do?

A
  • Best suited for load balancing HTTP/HTTPS traffic
  • application-aware (e.g. can sense when you change languages)
  • you can create advanced request routing, sending specific requests to specific web servers.
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6
Q

What does TCP stand for?

A

Transmission Control Protocol

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7
Q

What does a Network Load Balancer do?

A
  • best-suited for load balancing TCP traffic where extreme performance is required
  • capable of handling millions of requests per second, while maintaining ultra-low latencies
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8
Q

At what layer do ALBs operate?

A

Layer 7

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9
Q

At what layer do NLBs operate?

A

Layer 4

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10
Q

What are Classic Load Balancers?

A
  • Legacy Elastic Load Balancers
  • You can load balance HTTP/HTTPs Apps
  • Has some Layer 7 features and you can use some Layer 4 features
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11
Q

What will your load balancer return if your application is having issues?

A

A 504 Gateway timeout

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12
Q

What is the purpose of an X-Forwarded-For header?

A

If you need the IPv4 address of your end user

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13
Q

What are the two report out statuses for ELBs?

A
  • InService
  • OutofService
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14
Q

Do you get an IP address for your Load Balancers?

A

No; Load Balancers have their own DNS name

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15
Q

What do Sticky Sessions do?

A

They allow you to bind a user’s session to a specific EC2 instance, so that all requests from the user during the session are sent to the same instance.

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16
Q

Suppose you notice that all requests from a user are going to a single EC2 instance from an ELB. What might be causing this?

A

Sticky sessions are probably enabled

17
Q

Suppose Route53 is routing traffic evenly between two different availability zones, each of which has an ELB. The first AZ’s ELB is load-balancing 4 different EC2 instances, and the second AZ’s ELB is load-balancing just 1 EC2 instance. You want can you do to ensure that all 5 EC2 instances receive the same amount of traffic?

A

Turn on Cross Zone Load Balancing

18
Q

Suppose Route53 is routing all traffic to US-EAST-1A, where an ELB is load-balancing traffic between 4 different EC2 instances. For high availability, you bring up another EC2 instance in US-EAST-1B. How can you get the load balancer in US-EAST-1A to start sending traffic to the new EC2 instance?

A

Enable Cross Zone Load Balancing

19
Q

Suppose Route53 is routing all traffic to US-EAST-1A, where an ELB is load-balancing traffic between 4 different EC2 instances. You bring up another 2 EC2 instances in US-EAST-1B, your goal is to send traffic to www.myurl.com to one of the instances in US-EAST-1A, and traffic to www.myurl.com/images/ to one of the instances in US-EAST-1B. How can this be accomplished without creating new load balancers or changing anything in Route53?

A

Enable Path Patterns

20
Q

Suppose you are using a load balancer, but some of your user’s requests store information locally on the target EC2 instance, so you’ll need to ensure that your users stick to the same EC2 instance. How can you accomplish this?

A

Turn on Sticky Sessions

21
Q

What do Path Patterns do?

A

Path Patterns allow you to direct traffic to different EC2 instances based on the URL contained in the request

22
Q

What is Cross Zone Load Balancing?

A

Cross Zone Load Balancing enables you to load-balance across multiple AZs

23
Q

What is the value of Elastic Beanstalk?

A

With Elastic Beanstalk, you can quickly deploy and manage applications in the AWS Cloud without worrying about the infrastructure that runs those applications.

All you do is upload your application, and Elastic Beanstalk takes care of the rest (capacity provisioning, load balancing, scaling, application health monitoring, etc.)

24
Q

At a high level, what does CloudFormation do?

A

It is a way of completely scripting your cloud environment

25
Q

What, in the context of AWS, is Quick Start?

A

Quick Start is a bunch of CloudFormation templates already built by Solutions Architects, allowing you to create complex environments very quickly

26
Q

Can Elastic Beanstalk host Docker containers?

A

Yes

27
Q

What happens to a Docker container running in an Elastic Beanstalk environment if the container crashes or gets killed?

A

Elastic Beanstalk restarts it automatically

AWS Certified Solutions Architectn CO3 (59 decks)

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