PDF SOA-C02 Study Guide

To reduce latency in data transfer among EC2 instances, especially in high-performance computing (HPC) applications or applications requiring low network latency, using a placement group is the best approach:

Understanding Placement Groups:

A placement group in Amazon EC2 is a logical grouping of instances within a single Availability Zone. Using placement groups, you can achieve low-latency network performance necessary for tightly coupled node-to-node communication.

Types of Placement Groups:

Cluster Placement Group: Instances are physically located close together in the same Availability Zone to provide low-latency network performance.

Partition Placement Group: Instances are divided into logical segments called partitions, reducing the likelihood of simultaneous failures.

Spread Placement Group: Instances are placed on distinct underlying hardware to reduce correlated failures.

Creating and Using a Placement Group:

You can create a placement group using the AWS Management Console, AWS CLI, or AWS SDKs.

When launching instances, specify the placement group to ensure they are launched within the same group.

aws ec2 create-placement-group --group-name my-placement-group --strategy cluster

aws ec2 run-instances --image-id ami-12345678 --count 4 --instance-type c5.large --placement GroupName=my-placement-group

Relocating Existing Instances:

Stop the instances, modify the placement group settings, and then restart them. Note that not all instance types are supported within placement groups, so check the documentation for compatibility.

References:

Placement Groups

Cluster Instances for Low-Latency

To remotely connect to the EC2 instance, the SysOps administrator must ensure that the security group allows inbound SSH traffic.

Modify the Security Group:

Navigate to the EC2 console.

Select the security group associated with the EC2 instance.

Add an inbound rule to allow SSH traffic (TCP port 22) from the SysOps administrator's IP address.

Example rule:

Type: SSH

Protocol: TCP

Port Range: 22

Source:

Step-by-Step Explanation:

Understand the Problem:

The application read performance degrades when user connections exceed 200.

Need to automatically scale the database based on user demand.

Analyze the Requirements:

Implement auto scaling based on user connections to ensure optimal performance.

Evaluate the Options:

Option A: Migrate to a new Aurora multi-master DB cluster.

Multi-master clusters provide read and write scalability but may require significant changes to the application.

Option B: Modify the DB cluster to serverless mode.

Aurora Serverless provides automatic scaling, but it is more suitable for variable workloads with unpredictable demand.

Option C: Create an auto scaling policy with a target metric of 195 DatabaseConnections.

This directly addresses the need to scale based on user connections.

Auto scaling can add or remove replicas to maintain optimal performance.

Option D: Increase the Aurora Replica instance size.

This may improve performance but does not address scalability for sudden increases in user connections.

Select the Best Solution:

Option C: Creating an auto scaling policy with a target metric of 195 DatabaseConnections ensures the DB cluster scales automatically to handle increased load.

References:

Amazon Aurora Auto Scaling

Scaling Aurora DB Instances

Auto scaling based on DatabaseConnections ensures the Aurora DB cluster maintains optimal performance as user demand fluctuates.

Step-by-Step Explanation:

Understand the Problem:

A user cannot upload an object to an S3 bucket using a presigned URL, even though the URL is valid and the bucket has no policy applied.

Analyze the Requirements:

Determine the cause of the issue preventing the upload via the presigned URL.

Evaluate the Options:

Option A: The user has not properly configured the AWS CLI.

CLI configuration is not relevant to using a presigned URL.

Option B: The SysOps administrator does not have the necessary permissions.

The administrator's permissions are required to generate a valid presigned URL with sufficient permissions.

Option C: A bucket policy is required.

A bucket policy is not necessary if the presigned URL has the correct permissions.

Option D: The object has already been uploaded.

A presigned URL remains valid until it expires or the specified permissions are revoked.

Select the Best Solution:

Option B: Ensuring that the SysOps administrator has the necessary permissions to upload objects to the S3 bucket is crucial for generating valid presigned URLs.

References:

Amazon S3 Presigned URLs

IAM Policies for Amazon S3

The SysOps administrator must have the necessary permissions to upload objects to the S3 bucket, ensuring that the presigned URL generated allows the user to upload successfully.