AWS Certified Associate Changed SAA-C03 Questions

The solution that will reduce the launch time of the application during the next testing phase is to launch the EC2 On-Demand Instances with hibernation turned on and configure EC2 Auto Scaling warm pools. This solution allows the application to resume from a hibernated state instead of starting from scratch, which can save time and resources. Hibernation preserves the memory (RAM) state of the EC2 instances to the root EBS volume and then stops the instances.When the instances are resumed, they restore theirmemory state from the EBS volume and become productive quickly. EC2 Auto Scaling warm pools can be used to maintain a pool of pre-initialized instances that are ready to scale out when needed. Warm pools can also support hibernated instances, which can further reduce the launch time and cost of scaling out.

The other solutions are not as effective as the first one because they either do not reduce the launch time, do not guarantee availability, or do not use On-Demand Instances as required. Launching two or more EC2 On-Demand Instances with auto scaling features does not reduce the launch time of the application, as each instance still has to go through the initialization process. Launching EC2 Spot Instances does not guarantee availability, as Spot Instances can be interrupted by AWS at any time when there is a higher demand for capacity. Launching EC2 On-Demand Instances with Capacity Reservations does not reduce the launch time of the application, as it only ensures that there is enough capacity available for the instances, but does not pre-initialize them.

An Application Load Balancer (ALB) is a type of Elastic Load Balancer (ELB) that distributes incoming application traffic across multiple targets, such as EC2 instances, containers, Lambda functions, and IP addresses, in multiple Availability Zones1. An ALB can be internet-facing or internal. An internet-facing ALB has a public DNS name that clients can use to send requests over the internet1. An internal ALB has a private DNS name that clients can use to send requests within a VPC1. This solution meets the requirements of the question because:

It allows external internet traffic to connect to the web server on ports 80 and 443, as the ALB listens for requests on these ports and forwards them to the EC2 instance in the private subnet1.

It does not violate the corporate security mandate, as the EC2 instance is launched in a private subnet and does not have a public IPaddress or a route to an internet gateway2.

It reduces the operational overhead, as the ALB is a fully managed service that handles the tasks of load balancing, health checking, scaling, and security1.

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 NATgateways. 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

A write-through caching strategy adds or updates data in the cache whenever data is written to the database. This ensures that the data in the cache is always consistent with the data in the database. A write-through caching strategy also reduces the cache miss penalty, as data is always available in the cache when it is requested. However, a write-through caching strategy can increase the write latency, as data has to be written to both the cache and the database. A write-through caching strategy is suitable for applications that require high data consistency and low read latency.

A lazy loading caching strategy only loads data into the cache when it is requested, and updates the cache when there is a cache miss. This can result in stale data in the cache, as data is not updated in the cache when it is changed in the database. A lazy loading caching strategy is suitable for applications that can tolerate some data inconsistency and have a low cache miss rate.

An adding TTL caching strategy assigns a time-to-live (TTL) value to each data item in the cache, and removes the data from the cache when the TTL expires. This can help prevent stale data in the cache, as data is periodically refreshed from the database. However, an adding TTL caching strategy can also increase the cache miss rate, as data can be evicted from the cache before it is requested. An adding TTL caching strategy is suitable for applications that have a high cache hit rate and can tolerate some data inconsistency.

An AWS AppConfig caching strategy is not a valid option, as AWS AppConfig is a service that enables customers to quickly deploy validated configurations to applications of any size and scale. AWS AppConfig does not provide a caching layer for web applications.