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AWS Architect Exam > High Availability Architecture > Flashcards

High Availability Architecture Flashcards

1
Q

What are the 3 different types of Load Balancer in AWS?

A

The 3 different types of Load Balancer are:

  • Application Load Balancer
  • Network Load Balancer
  • Classic Load Balancer
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2
Q

What are Application Load Balancers best suited for?

A

Application Load Balancers are best suited for the load balancing of http and https traffic

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3
Q

What are Network Load Balancers best suited for?

A

Network Load Balancers are best suited for the load balancing of TCP traffic where extreme performance is required.

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4
Q

What are Classic Load Balancers best suited for?

A

Classic Load Balancers are best suited for when costs need to be kept low.

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5
Q

What would you do if the ELB (Classic) responds with a 504 error?

A

If your ELB has a 504 error this means the application is having issues. This could be either the web server or db layer.

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6
Q

What is X-forwarded-for?

A

X-forwarded-for is used to identify the original IPv4 address of the client after the traffic has come through an ELB

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7
Q

How do ELBs validate whether an instance is healthy or not?

A

ELBs conduct health checks to define whether instances are reported as Inservice or OutofService

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8
Q

Are ELBs given default IP addresses?

A

ELBs do not have IP addresses instead they are given their own DNS names.

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9
Q

What are sticky sessions?

A

Sticky sessions allow you to bind a users session to a specific EC2 instance. This ensures that responses to user requests are sent back to the same user.

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10
Q

With which type of ELBs would you use sticky sessions?

A

You would use sticky sessions with Classic Load Balancers

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11
Q

What would you do if one of your instances behind a Classic Load Balancer was not receiving any traffic?

A

If one instance was receiving no traffic then you should disable sticky sessions.

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12
Q

What is cross-zone load balancing?

A

Cross-zone load balancing is the ability to balance traffic across regions.

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13
Q

What are Path Patterns?

A

Path Patterns is when you forward-on traffic based on the url path. So for example, one type of request can go to one target group and another type of request go to another.

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14
Q

What is auto-scaling?

A

Auto Scaling monitors your applications and automatically adjusts capacity to maintain steady, predictable performance at the lowest possible cost.

The service provides a simple, powerful user interface that lets you build scaling plans for resources including Amazon EC2 instances and Spot Fleets.

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15
Q

What are the 3 components of auto-scaling?

A

The 3 components of auto-scaling are:

  • Groups
  • Configuration Templates
  • Scaling Options
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16
Q

What are the auto-scaling options?

A

Auto-scaling options are:

  • Maintain current instance levels at all times
  • Scale manually
  • Scale based on a schedule
  • Scale based on demand
  • Use predictive scaling
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17
Q

What is manual scaling?

A

Manual scaling is when you manually chose to maximum, minimum or desired capacity of your group.

18
Q

What is auto-scaling based on demand?

A

Auto-scaling based on demand is when you ask AWS to maintain a number of instances based on a set CPU utilisation number etc

19
Q

In Cloud terms, what is durability?

A

Durability refers to the on-going existence of the object or resource.

Note that it does not mean you can access it, only that it continues to exist.

20
Q

In Cloud terms, what is resiliency?

A

Resiliency is the ability of a workload to recover from infrastructure or service disruptions, dynamically acquire computing resources to meet demand, and mitigate disruptions, such as misconfigurations or transient network issues.

21
Q

In Cloud terms, what is availability?

A

Availability can be described as the % of a time period when the service will be able to respond to your request in some fashion.

22
Q

What in Cloud terms, what is reliability?

A

Reliability is the probability that a system will work as designed.

23
Q

Why can’t you use an Application Load balancer when creating a pair of highly available bastion servers?

A

Application Load balancers work at layer 7, the traffic into bastions would need to be balanced at layer 4.

24
Q

Is it cheaper to utilise 2 Bastions behind a Network Load Balancer or use an auto-scaling group to manage a single host?

A

It is cheaper to use the auto-scaling group option but this isn’t 100% fault tolerant because if the instance fails, it will take time for it to be replaced by the auto-scaling group.

25
Q

What happens in the event of an unplanned outage to your RDS instance?

A

In the even of an unplanned outage to your RDS instance AWS switches to a standby replica in another AZ (if multi-AZ has been enabled)

26
Q

What is the difference between scaling-up and scaling-out?

A

Scaling out is where you have more of the same resource separately working in parallel (visualize services sitting side by side).

Scaling Up is where you make it bigger and bigger like an ugly tower with more floors being added after the initial design was finished

27
Q

How many running instances is the maximum supported by a spread placement group?

A

A spread placement group supports a maximum of seven running instances per availability zone

28
Q

Can you use the standby database instance to offload reads to help with performance?

A

You cannot use the standby instance to offload reads. The secondary database is there only for failover.

29
Q

What is a benefit of cross-zone load balancing?

A

Cross-zone load balancing reduces the need to maintain equivalent numbers of instances in each enabled Availability Zone, and improves your application’s ability to handle the loss of one or more instances.

30
Q

What does CloudFormation enable?

A

CloudFormation is a way of completely scripting your cloud environment.

31
Q

What is CloudFormation Quick Start?

A

CloudFormation QuickStart is a bunch of CloudFormation templates built by AWS Architects that allow you to create complex environments quickly

32
Q

What is Elastic Beanstalk?

A

Elastic Beanstalk is an enabler to quickly deploy and manage applications in AWS without worrying about the underlying architecture.

With Elastic Beanstalk you just need to upload your application and Elastic Beanstalk automatically handles the details of capacity provisioning, load balancing, scaling and application health monitoring

33
Q

What AWS services can be used on-premise?

A

The following AWS services can be used on-premise:

  • Database Migration Service (DMS)
  • Server Migration Service (SMS)
  • AWS Directory Service
  • VM Import/Export
  • Download Amazon Linux 2 as an ISO
34
Q

What is DMS?

A

Database Migration Service allows you to move databases to and from AWS

A typical use case is to enable a DR environment in AWS and on-premise as your primary.

35
Q

What is the Server Migration Service?

A

AWS Server Migration Service (AWS SMS) automates the migration of your on-premises VMware vSphere, Microsoft Hyper-V/SCVMM, and Azure virtual machines to the AWS Cloud.

This can be used as a backup tool, a DR tool, and as a part of a multi-site strategy

36
Q

What is AWS Application Directory Service?

A

AWS Application Directory Service helps customers to plan for migration to the Cloud by gathering information about their on-premise data centres

37
Q

How does the Application Directory Service work?

A

You install an Application Directory agentless connector as a virtual appliance and it will then build a server utilisation and dependency map of your on-premise environment.

The output can also be used to estimate the Total Cost of Ownership

38
Q

How can you use VM Import/Export?

A

You can use VM Import/Export to migrate existing applications in to EC2.

It can be used to create a DR strategy on AWS or use AWS as a second site. It can also be used to export your VMs to your on-premise data centre

39
Q

What layers do ALBs and NLBs/CLBs work at?

A

ALBs work at layer 7 (http and https) and NLBs/CLBs work at layer 4 (TCP traffic)

40
Q

Which type of Load Balancer may by mistake send traffic to an unavailable endpoint?

A

An NLB may send traffic to an unavailable endpoint because it works at Level 4 rather than 7 and so cannot tell what is happening at the application layer

41
Q

What do you need in order to create and use a Load Balancer?

A

In order to use a Load Balancer you need at least two public-facing subnets

42
Q

What tool can identify the source of your traffic and direct it to the correct language version of your website?

A

An Application Load balancer can direct traffic to certain instances based upon the traffic itself

AWS Architect Exam (11 decks)

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