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AWS Certified Solutions Architect - Associate > High Availability & Scaling > Flashcards

High Availability & Scaling Flashcards

1
Q

What does CloudFront provide?

A

A content delivery network (CDN) that caches content globally - as close to the end users as possible to improve performance.

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2
Q

What are the three types of Elastic Load Balancer (ELB) available in AWS?

A
  1. Application Load Balancer (ALB) - Layer 7, HTTP/S and WebSocket
  2. Network Load Balancer (NLB) - Layer 4, TCP, UDP, and TLS
  3. Classic Load Balancer (CLB) - V1, lacks features, 1 SSL cert per CLB, shouldn’t be used anymore
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3
Q

What happens when an Elastic Load Balancer (ELB) is created?

A

ELB nodes are placed in two (required) or more subnets in each AZ that the ELB services. These nodes automatically scale within the AZ.

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4
Q

What type of DNS record is an Elastic Load Balancer (ELB) configured with and where does it resolve to?

A

An A record that resolves to all the ELB’s nodes.

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5
Q

What are Internet-facing Elastic Load Balancer (ELB) nodes given that internal ELB nodes are not?

A

Public IPs.

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6
Q

Can Internet-facing Elastic Load Balancer (ELB) connect to public EC2 instances or private EC2 instances?

A

Both.

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7
Q

How many free IPs per subnet are required for an Elastic Load Balancer (ELB)?

A

An ELB needs at least eight free IPs per subnet so it can scale. A /27 subnet is recommended.

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8
Q

What does cross-zone load balancing enable?

A

It allows a ELB node in one AZ to direct traffic to resources in another AZ. This is enabled by default.

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9
Q

What does a logical Elastic Load Balancer (ELB) represent?

A

A DNS A record pointing at 1+ ELB nodes per subnet.

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10
Q

To work with an Internet-facing Elastic Load Balancer (ELB), does an EC2 instance need to be public or private?

A

Either. The EC2 instance doesn’t need to be public to work with an ELB.

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11
Q

What types of Layer 7 data can an Application Load Balancer (ALB) inspect?

A

Content type, cookies, custom headers, user location, and app behavior.

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12
Q

Where do SSL/TLS session terminate when using an Application Load Balancer (ALB)?

A

On the ALB. There is no unbroken SSL. A new connection will be made to the application. This means ALBs must have SSL certs for HTTPS.

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13
Q

Which type of Elastic Load Balancer (ELB) is faster? A Network Load Balancer or an Application Load Balancer?

A

A Network Load Balancer is faster because it works at the Network Layer rather than the Application Layer.

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14
Q

What do Application Load Balancer rules do?

A

They inspect conditions (such as host-header, http-header, http-request-method, query-string, and source-ip) and take actions (such as forward, redirect, authenticate-oidc, authenticate-cognito) based on those conditions.

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15
Q

If you have to forward connections through an Elastic Load Balancer (ELB) without breaking the SSL connection, what type of ELB must you use?

A

Network Load Balancer.

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16
Q

What type of Elastic Load Balancer (ELB) should you likely use if you are loading balancing connections that DO NOT use HTTP/HTTPS?

A

Network Load Balancer.

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17
Q

If you need to use a static IP for whitelisting, what type of Elastic Load Balancer (ELB) should you use?

A

Network Load Balancer.

18
Q

If performance and throughput are critical to your application, what type of Elastic Load Balancer (ELB) should you use?

A

Network Load Balancer.

19
Q

If you need to use PrivateLink, what type of Elastic Load Balancer (ELB) should you use?

A

Network Load Balancer.

20
Q

What to Launch Configurations and Launch Templates provide?

A

A way to define the configuration of an EC2 in advance. This includes AMI, Instance Type, Storage, Key pair, networking, security groups, and Userdata.

21
Q

Can Launch Configurations and Launch Templates be edited?

A

No. Once created, they cannot be changed.

22
Q

What do Auto Scaling Groups provide?

A

Automatic Scaling for EC2. This also can be used for self-healing of EC2.

23
Q

How do Auto Scaling Groups know what EC2 instance to provision?

A

Using Launch Templates or Launch Configurations.

24
Q

How does an Auto Scaling Group keep the number of EC2 instances at the desired capacity?

A

By provisioning or terminating instances as dictated by the minimum, desired, and maximum size specified for the Auto Scaling Group.

25
Q

What do Scaling Policies do?

A
  1. Dynamic scaling using metrics like CPU usage
  2. Scheduled scaling
  3. Manual scaling
26
Q

Where are Auto Scaling Group configured?

A

Across one or many AZ’s. The ASG is linked to a VPC and subnets from that VPC are configured on the ASG. EC2 instances will be placed in those subnets (best effort at spreading them evenly).

27
Q

How do you ensure your Auto Scaling Group doesn’t scale too quickly and before a metric changes in response to a scaling action?

A

Cooldown Periods can be specified in a Scaling Policy that hold off on any new scaling actions for a specified period of time. This allows the metric time to change before another scaling action takes place.

28
Q

How do you scale when using an Elastic Load Balancer (ELB)?

A

By adding an Auto Scaling Group to the ELB’s target group.

29
Q

What is Target Tracking for Auto Scaling Groups?

A

You set a target value for a metric and the ASG will scale in or out to try and keep the metric at the specified value.

30
Q

Why is step scaling preferable to simple scaling?

A

It allows you to handle large increase and large decreases in load more appropriately.

31
Q

What do Auto Scaling Group Lifecycle Hooks do?

A

Hook into a provision or terminate event and pause the action for a period of time so that some custom action can be taken.

32
Q

What do Auto Scaling Groups Health Checks do?

A

They determine if an instance is healthy. If it is not, it will terminate the instance and replace it for self healing.

33
Q

How do you prevent a newly provisioned EC2 instance that is bootstrapping from being terminated by an Auto Scaling Group Health Check because it is seen as unhealthy?

A

By configuring a health check grace period that will institute a delay before health checks are started for the newly provisioned instance.

34
Q

What are the three types of SSL Offload used by an Elastic Load Balancer (ELB)?

A
  1. Bridging (terminated HTTPS)
  2. Pass-through (unbroken HTTPS)
  3. Offload (SSL then HTTP)
35
Q

What is SSL Bridging for an Elastic Load Balancer (ELB)?

A

The listener is configured for HTTPS and the connection terminates on the ELB. The ELB then initiates a new SSL connection to backend instances. Each backend instance needs to perform cryptographic operations on the new SSL connection.

36
Q

What is SSL Pass-through for an Elastic Load Balancer (ELB)?

A

Using a network load balance, the SSL connection is just passed through to the backend instance without terminating the SSL connection. Each backend instance needs to perform cryptographic operations on the SSL connection.

37
Q

What is SSL Offload for an Elastic Load Balancer (ELB)?

A

The listener is configured for HTTPS and the connection terminates on the ELB. The ELB then initiates an HTTP unencrypted connection to backend instances. No cryptographic operations are needed on the backend instance.

38
Q

What is Session Stickiness for an Application Load Balancer?

A

The ALB generates a cookie that locks the user to a single backend instance for a specified duration (1 second to 7 days).

39
Q

What problem can Session Stickiness cause of Application Load Balancers?

A

Uneven load on the backend instances because users are locked to specific instances for their sessions.

40
Q

When would you use a Gateway Load Balancer?

A

When you need to run and scale 3rd party applications like firewalls, IDSs, and IDPs and unaltered packets need to be load balanced across horizontally scaling appliances.

41
Q

Which supports versioning? Launch Configurations or Launch Templates?

A

Launch Templates.

42
Q

Which can be used to launch EC2 instances directly? Launch Configurations or Launch Templates?

A

Launch Templates.

AWS Certified Solutions Architect - Associate (49 decks)

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