I was tempted to pick A but then I realized there are two key requirements: - scale seamlessly - cost-effectively None of A-C give seamless scalability. A and B are about adding second instance (which I assume does not match to "scale seamlessly"). C is about changing instance type. Therefore D is only workable solution to the scalability requirement

I wouldn't run my website on spot instances. Spot instances might be terminated at any time, and since I need to run analytics application it's not an option for me. And using route 53 for load balancing of 2 instances is an overkill. I go with A.

PHP....

I'll pick D because it sounds fun :)

"Scale seamlessly", none of A-C include scaling at all.

spot instance receives 2 minutes interruption notice, it should be enough for requests to finish, it's quite unusal for app to run longer requests only option D allow for seamless scaling with autoscaling group

Option B is a cost-effective choice that combines the benefits of database migration to RDS, horizontal scaling with EC2 instances, and control over traffic distribution with Route 53 weighted routing, making it the best solution for the given requirements.

Scale seamlessly = Autoscaling group, Amazon Aurora MySQL DB instance Cost effective = Spot Fleet

The key reasons are: Migrating the database to Amazon Aurora MySQL provides a scalable, high performance database to support the application. Creating an AMI of the web application and using it in an Auto Scaling group with Spot instances allows cheap and efficient scaling of the web tier. The Application Load Balancer distributes traffic across the Auto Scaling group. Spot instances in an Auto Scaling group allow cost-optimized automatic scaling based on demand. This approach provides high availability and seamless scaling without manual intervention.

D is correct because migrating the database to Amazon Aurora provides better scalability and performance compared to Amazon RDS for MySQL. Creating an AMI of the web application allows for easy replication of the application on multiple instances. Using a launch template and Auto Scaling group with Spot Fleet provides cost optimization by leveraging spot instances. Adding an Application Load Balancer ensures the load is distributed across the instances for seamless scaling. A is incorrect because using an Application Load Balancer with multiple EC2 instances is a better approach for scalability compared to relying on a single instance. B is incorrect because weighted routing in Amazon Route 53 distributes traffic based on fixed weights, which may not dynamically adjust to the changing load. C is incorrect because using AWS Lambda to stop and change the instance type based on CPU utilization is not an efficient way to handle scaling for a web application. Auto Scaling is a better approach for dynamic scaling.

the options that said "launch a second EC2", have no sense ... why 2?, why not 3 or 4 or 5? so options A and B drop. C is no sense (Lambda doing this like a Scaling Group?, absurd) Has to be D. Little extrange cos' Aurora is a very good solution, but NOT CHEAP (remember: cost-effectively). To be honest, the most cost-effectively is B je je

A Spot Fleet is a set of Spot Instances and optionally On-Demand Instances that is launched based on criteria that you specify. The Spot Fleet selects the Spot capacity pools that meet your needs and launches Spot Instances to meet the target capacity for the fleet. By default, Spot Fleets are set to maintain target capacity by launching replacement instances after Spot Instances in the fleet are terminated. You can submit a Spot Fleet as a one-time request, which does not persist after the instances have been terminated. You can include On-Demand Instance requests in a Spot Fleet request.

Ans: D Both Amazon RDS for MySQL and Amazon Aurora MySQL are designed to provide customers with fully managed relational database services, but Amazon Aurora MySQL is designed to provide better performance, scalability, and reliability, making it a better option for customers who need high-performance database services.

Using an Auto Scaling group with a launch template and a Spot Fleet allows the company to scale the application seamlessly and cost-effectively, by automatically adding or removing instances based on the demand, and using Spot instances which are spare compute capacity available in the AWS region at a lower price than On-Demand instances. And also by migrating the database to Amazon Aurora MySQL DB instance, it provides higher scalability, availability, and performance than traditional MySQL databases.

The answer is D: Migrate the database to Amazon Aurora MySQL - this will let the DB scale on it's own; it'll scale automatically without needing adjustment. Create AMI of the web app and using a launch template - this will make the creating of any future instances of the app seamless. They can then be added to the auto scaling group which will save them money as it will scale up and down based on demand. Using a spot fleet to launch instances- This solves the "MOST cost-effective" portion of the question as spot instances come at a huge discount at the cost of being terminated at any time Amazon deems fit. I think this is why there's a bit of disagreement on this. While it's the most cost effective, it would be a terrible choice if amazon were to terminate that spot instance during a busy period.

But I have a question, For Spot instance, is it possible that at some time there is no spot resources available at all? because it is not guaranteed, right?

Option D is the most cost-effective solution that meets the requirements. Migrating the database to Amazon Aurora MySQL will allow the database to scale automatically, so it can handle an increase in traffic without manual intervention. Creating an AMI of the web application and using a launch template will allow the company to quickly and easily launch new instances of the application, which can then be added to an Auto Scaling group. This will allow the application to automatically scale up and down based on demand, ensuring that there are enough resources to handle busy times without incurring the cost of running idle resources. Using a Spot Fleet to launch the instances will allow the company to take advantage of Amazon's spare capacity and get a discount on their EC2 instances. Attaching an Application Load Balancer to the Auto Scaling group will allow the load to be distributed across all of the available instances, improving the performance and reliability of the application.