AWS Certified Associate SAA-C03 Amazon Web Services Study Notes

A public NAT gateway enables instances in a private subnet to send outbound traffic to the internet, while preventing the internet from initiating connections with the instances. A public NAT gateway requires an elastic IP address and a route to the internet gateway for the VPC. A private NAT gateway enables instances in a private subnet to connect to other VPCs or on-premises networks through a transit gateway or a virtual private gateway. A private NAT gateway does not require an elastic IP address or an internet gateway. Both private and public NAT gateways map the source private IPv4 address of the instances to the private IPv4 address of the NAT gateway, but in the case of a public NAT gateway, the internet gateway then maps the private IPv4 address of the public NAT gateway to the elastic IP address associated with the NAT gateway. When sending response traffic to the instances, whether it’s a public or private NAT gateway, the NAT gateway translates the address back to the original source IP address.

Creating public NAT gateways in the same private subnets as the EC2 instances (option A) is not a valid solution, as the NAT gateways would not have a route to the internet gateway. Creating private NAT gateways in the same private subnets as the EC2 instances (option B) is also not a valid solution, as the instances would not be able to access the internet through the private NAT gateways. Creating private NAT gateways in public subnets in the same VPCs as the EC2 instances (option D) is not a valid solution either, as the internet gateway would drop the traffic from the private NAT gateways.

Therefore, the only valid solution is to create public NAT gateways in public subnets in the same VPCs as the EC2 instances (option C), as this would allow the instances to access the internet through the public NAT gateways and the internet gateway. References:

• NAT gateways - Amazon Virtual Private Cloud
• NAT gateway use cases - Amazon Virtual Private Cloud
• Amazon Web Services – Introduction to NAT Gateways
• What is AWS NAT Gateway? - KnowledgeHut

To provide individual and secure URLs for all customers using an API Gateway REST API, you need to do the following steps:

• A. Register the required domain in a registrar. Create a wildcard custom domain name in a Route 53 hosted zone and record in the zone that points to the API Gateway endpoint. This step will allow you to use a custom domain name for your API instead of the default one generated by API Gateway. A wildcard custom domain name means that you can use any subdomain under your domain name (such as customer1.example.com or customer2.example.com) to access your API. You need to register your domain name with a registrar (such as Route 53 or a third-party registrar) and create a hosted zone in Route 53 for your domain name. You also need to create a record in the hosted zone that points to the API Gateway endpoint using an alias record.
• D. Request a wildcard certificate that matches the custom domain name in AWS Certificate Manager (ACM) in the same Region. This step will allow you to secure your API with HTTPS using a certificate issued by ACM. A wildcard certificate means that it can match any subdomain under your domain name (such as *.example.com). You need to request or import a certificate in ACM that matches your custom domain name and verify that you own the domain name. You also need to request the certificate in the same Region as your API.
• F. Create a custom domain name in API Gateway for the REST API. Import the certificate from AWS Certificate Manager (ACM). This step will allow you to associate your custom domain name with your API and use the certificate from ACM to enable HTTPS. You need to create a custom domain name in API Gateway for the REST API and specify the certificate ARN from ACM. You also need to create a base path mapping that maps a path from your custom domain name to your API stage.

References: https://docs.aws.amazon.com/apigateway/latest/developerguide/how-to-custom-domains.html https://docs.aws.amazon.com/acm/latest/userguide/gs-acm-request.html

AWS Lambda is a serverless compute service that lets you run code without provisioning or managing servers. You can use Lambda to create and test microservices that are written in Python or other supported languages. Lambda scales automatically to handle the number of requests per second. You only pay for the compute time you consume. Lambda also integrates with other AWS services, such as Amazon API Gateway, Amazon S3, Amazon DynamoDB, and Amazon SQS, to enable event-driven architectures. Lambda has minimal infrastructure and operational overhead, as you do not need to manage servers, operating systems, patches, or scaling policies.

The other options are not serverless solutions and require more infrastructure and operational support. They also do not scale automatically to handle the number of requests per second. A Spot Fleet is a collection of EC2 instances that run on spare capacity at low prices. However, Spot Instances can be interrupted by AWS at any time, which can affect the availability and performance of your microservice. AWS Elastic Beanstalk is a service that automates the deployment and management of web applications on EC2 instances. However, you still need to provision, configure, and monitor the underlying EC2 instances and load balancers. Amazon EKS is a service that runs Kubernetes on AWS. However, you still need to create, configure, and manage the EC2 instances that form the Kubernetes cluster and nodes. You also need to install and update the Kubernetes software and tools.

References:

• What is AWS Lambda?
• Building Lambda functions with Python
• Create a layer for a Lambda Python function
• AWS Lambda – Function in Python
• How do I call my AWS Lambda function from a local python script?

S3 Storage Lens is a fully managed S3 storage analytics solution that provides a comprehensive view of object storage usage, activity trends, and recommendations to optimize costs. Storage Lens allows you to analyze object access patterns across all of your S3 buckets and generate detailed metrics and reports.