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AWS Professional > 05 Compute Scalability > Flashcards

05 Compute Scalability Flashcards

1
Q

Describe the On-demand purchase option for EC2.

A

On-demand is the default purchase option that allows immediate access to EC2 instances without any long-term commitment.

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2
Q

How does the Spot purchase option work in EC2?

A

Spot offers surplus capacity at a discount, where users bid a maximum price, but are charged the actual spot price. Instances run until the spot price exceeds the maximum bid.

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3
Q

What are Spot interruption notices in EC2?

A

Spot interruption notices provide a two-minute advance warning of interruptions, accessible via IMDS on the instance or EventBridge.

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4
Q

Define Reserved instances in EC2.

A

Reserved instances provide discounts for long-term, consistent usage commitments, which can be tied to specific instance types and availability zones.

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5
Q

How can smaller Reserved instances affect larger instances in EC2?

A

Smaller Reserved instances can partially cover the costs of larger instances, such as a reservation for an m5.xlarge partially offsetting the cost of an m5.2xlarge.

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6
Q

What are Scheduled reservations in EC2?

A

Scheduled reservations are long-term commitments for usage during specific time windows, such as daily or weekly.

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7
Q

Describe Dedicated hosts in EC2.

A

Dedicated hosts provide access to single-tenant hardware, with pricing based on the host, allowing instances to be launched on top of it, useful for licensing that depends on physical machines.

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8
Q

What is the purpose of Dedicated instances in EC2?

A

Dedicated instances automatically assign instances to hosts, ensuring that hosts are not shared with other customers, primarily for compliance reasons.

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9
Q

How do On-demand capacity reservations work in EC2?

A

On-demand capacity reservations reserve capacity for EC2 instances, but the on-demand rate is billed even if the reserved capacity is not used.

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10
Q

Define Savings plans in the context of EC2.

A

Savings plans are 1 or 3 year commitments for hourly spend that offer more flexibility and can be applied to EC2, Fargate, and Lambda.

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11
Q

What are ENIs in EC2?

A

ENIs, or Elastic Network Interfaces, are virtual interfaces used for networking in EC2 instances.

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12
Q

How is the primary ENI related to an EC2 instance?

A

The primary ENI is tied to the lifecycle of the EC2 instance, meaning it is created and deleted with the instance.

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13
Q

Describe the characteristics of Secondary ENIs in AWS.

A

Secondary ENIs can be added at any time, must be in the same Availability Zone (AZ), and can link to other subnets. Security groups are attached to ENIs, not instances.

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14
Q

How does the private IP address of an ENI behave during instance restarts?

A

The private IP address of an ENI is static and does not change when the instance restarts.

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15
Q

Define the SRC/DST check in relation to ENIs.

A

The SRC/DST check drops packets if the source or destination address isn’t on the ENI. It should be disabled for self-hosted NAT and similar configurations.

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16
Q

What are the two methods to customize EC2 instances with software?

A

The two methods are Bootstrapping using custom user data and AMI baking, which uses a custom AMI created from an instance with the software installed.

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17
Q

How does AMI baking benefit instance readiness?

A

AMI baking allows instances to be ready faster, making it ideal for scenarios like autoscaling.

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18
Q

Describe the purpose of placement groups in AWS.

A

Placement groups influence where instances are physically placed to optimize performance, such as minimizing network latency or ensuring instances run on different hardware.

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19
Q

What is the function of a Cluster placement group?

A

A Cluster placement group packs instances close together to minimize inter-instance network latency, ideally with the same instance type and started at the same time.

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20
Q

Explain the goal of a Spread placement group.

A

A Spread placement group aims to ensure that every instance runs on different hardware, and it can span multiple Availability Zones (AZs) with a limit of 7 instances per AZ.

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21
Q

Define Partition placement groups and their characteristics.

A

Partition placement groups launch instances into isolated partitions, with a maximum of 7 partitions per AZ, allowing unlimited instances to be launched per partition.

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22
Q

How does the DNS name of an ALB function in AWS?

A

The DNS name of an Application Load Balancer (ALB) resolves to the nodes located in the ALB’s subnets, which have public and private IPs unless the ALB is set to internal.

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23
Q

What is the minimum requirement for IPs available for a load balancer?

A

At a minimum, 8 IPs must be available for the load balancer, but more should be available for scaling.

24
Q

Describe the concept of cross-zone load balancing.

A

Cross-zone load balancing allows nodes in one Availability Zone (AZ) to direct traffic to nodes in another AZ, enhancing load distribution.

25
Q

Describe the purpose of Network Load Balancers (NLBs).

A

NLBs are used for non-HTTP(s) traffic such as UDP and SSH, and they are required when a static IP is needed.

26
Q

How does the deregistration delay function in load balancing?

A

The deregistration delay allows in-flight connections to complete for a certain period of time after a target is deregistered, with the default period being 300 seconds.

27
Q

Define the X-Forwarded-For header and its purpose.

A

The X-Forwarded-For header allows the target to see the IP of the original requestor, appending multiple hops to a list of IPs if applicable.

28
Q

Explain the PROXY protocol and its relation to NLBs.

A

The PROXY protocol is similar to X-Forwarded-For but operates at Layer 4, making it compatible with Network Load Balancers.

29
Q

What is the role of Gateway Load Balancers (GWLB)?

A

GWLBs are used for running third-party appliances that inspect traffic, such as firewalls and intrusion detection systems.

30
Q

How does the GENEVE tunneling protocol function in Gateway Load Balancers?

A

The GENEVE tunneling protocol ensures that traffic packets are not modified during transmission.

31
Q

Describe flow stickiness in the context of Gateway Load Balancers.

A

Flow stickiness ensures that traffic from one source is consistently sent to the same appliance.

32
Q

What is the function of Autoscaling Groups (ASGs)?

A

ASGs maintain the number of running instances at the desired capacity based on a single launch configuration or launch template version.

33
Q

How do scaling policies work in Autoscaling Groups?

A

Scaling policies adjust the desired capacity of ASGs to match demand, using either scheduled scaling for time-based adjustments or dynamic scaling based on metrics.

34
Q

Define simple scaling in the context of dynamic scaling.

A

Simple scaling uses straightforward rules based on CloudWatch Metrics to make scaling decisions.

35
Q

Describe stepped scaling in the context of auto-scaling groups.

A

Stepped scaling is a method that adjusts the size of the response based on how far the metric is from the expected value, allowing for more nuanced scaling actions.

36
Q

How does target tracking work in auto-scaling groups?

A

Target tracking automatically makes adjustments to maintain a specified metric at a target value, ensuring optimal performance.

37
Q

Define the cooldown period in auto-scaling.

A

The cooldown period specifies a time to wait after one scaling action before performing another, preventing rapid scaling actions that could destabilize the system.

38
Q

What are lifecycle hooks in auto-scaling groups?

A

Lifecycle hooks allow custom actions to take place when an instance launches or is terminated, enabling additional processes during these events.

39
Q

Explain how auto-scaling groups handle unhealthy instances.

A

Auto-scaling groups automatically replace unhealthy instances using EC2 health checks, ELB health checks, or custom health checks to ensure system reliability.

40
Q

What is the purpose of EC2 health checks in auto-scaling?

A

EC2 health checks ensure that the instance is ‘RUNNING’ and passes its instance status checks, helping to identify and replace unhealthy instances.

41
Q

Describe the function of ELB health checks in auto-scaling groups.

A

ELB health checks ensure that the instance is ‘RUNNING’ and passing its Elastic Load Balancer health checks, contributing to the overall health of the application.

42
Q

What are custom health checks in the context of auto-scaling?

A

Custom health checks allow an external monitoring system to label the health of instances, providing flexibility in health assessment.

43
Q

Define the grace period in auto-scaling groups.

A

The grace period, which defaults to 300 seconds, is a time during which health checks are ignored, allowing the instance time to bootstrap and become operational.

44
Q

How are Lambda versions and aliases different?

A

Lambda versions are immutable, meaning they cannot be changed once created, while aliases can be adjusted to point to different versions or perform weighted routing.

45
Q

What role does the Systems Manager Agent play in AWS?

A

The Systems Manager Agent manages AWS and on-premises infrastructure, maintaining an inventory of installed software, patching instances, and running commands.

46
Q

Explain the connection process for on-premises instances using Systems Manager.

A

On-premises instances are connected using an activation code and an IAM Anywhere role, allowing them to be managed through AWS Systems Manager.

47
Q

What is the purpose of Session Manager in AWS Systems Manager?

A

Session Manager securely connects to EC2 instances, providing a way to manage and interact with instances without needing SSH access.

48
Q

Describe the purpose of the SSM VPCe.

A

The SSM VPCe is used for instances in private VPCs.

49
Q

How does Run Command facilitate command execution?

A

Run Command allows command documents to be executed at scale, targeting single instances or groups based on tagging or resource groups.

50
Q

Define concurrency in the context of Run Command.

A

Concurrency controls how many instances are targeted in parallel during command execution.

51
Q

What is the role of the error threshold in Run Command?

A

The error threshold controls how many individual executions can fail before the overall process is stopped.

52
Q

Explain how Patch Manager utilizes Run Command.

A

Patch Manager uses the Run Command to ensure instances meet the patch baseline.

53
Q

What are maintenance windows in Patch Manager?

A

Maintenance windows can be configured to avoid business hours and are where the targets, known as patch groups, are set.

54
Q

How does inventory function in Patch Manager?

A

Inventory ensures that the patches were applied correctly to the instances.

55
Q

What is an example of a patch baseline provided by AWS?

A

An example of a patch baseline is AWS-AmazonLinux2DefaultPatchBaseline, which includes critical and security updates.

56
Q

Describe the coverage of the AWS-WindowsPredifinedPatchBaseline-OS-Applications.

A

The AWS-WindowsPredifinedPatchBaseline-OS-Applications covers both the operating system and Microsoft applications.

AWS Professional (11 decks)

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