The question asks for the service that may NOT be required by the user when architecting for an automatically scalable application.; S3 is not required, and thus is the correct answer.; The user can achieve automated scalability by configuring the AutoScaling service to run the required number of EC2 instances based on the conditions that he define. Cloudwatch is used to monitor the utilization of the running instances and allow AutoScaling to automatically scale up (by launching more instances) or down (by terminating instances) based on changes on demand.; Based on the application requirements, a developer may decide not to use S3. The storage resource in this case will be the EBS volumes that are attached to the Amazon EC2 instances.; References:; https://aws.amazon.com/autoscaling/; https://aws.amazon.com/cloudwatch/; https://aws.amazon.com/ec2/

** Scaling Vertically:; Scaling vertically takes place through an increase in the specifications of an individual resource (e.g., upgrading a server with a larger hard drive, adding more memory, or provisioning a faster CPU). On Amazon EC2,this can easily be achieved by stopping an instance and resizing it to an instance type that has more RAM, CPU, IO,or networking capabilities. This way of scaling can eventually hit a limit and it is not always a cost efficient or highly available approach. However, it is very easy to implement and can be sufficient for many use cases especially in the short term.; ** Scaling Horizontally:; Scaling horizontally takes place through an increase in the number of resources (e.g., adding more hard drives to a storage array or adding more servers to support an application). This is a great way to build Internet-scale applications that leverage the elasticity of cloud computing.; References:; https://d1.awsstatic.com/whitepapers/AWS_Cloud_Best_Practices.pdf

AWS X-Ray helps developers analyze and debug production, distributed applications, such as those built using a microservices architecture. With X-Ray, you can understand how your application and its underlying services are performing to identify and troubleshoot the root cause of performance issues and errors. X-Ray provides an end-to-end view of requests as they travel through your application, and shows a map of your application’s underlying components. You can use X-Ray to analyze both applications in development and in production, from simple three-tier applications to complex microservices applications consisting of thousands of services.; Option A is not correct. AWS OpsWorks is a configuration management service that provides managed instances of Chef and Puppet.; Option B is not correct. The main purpose of the AWS CloudWatch is to monitor the utilization of your AWS resources.; Option C is not correct. Amazon Aurora is a database service.; References:; https://aws.amazon.com/xray/

You don’t have to pay any fees when terminating your EC2 Instances.; References:; https://aws.amazon.com/ec2/pricing/

AWS CloudFormation is a service that helps you model and set up your Amazon Web Services resources so that you can spend less time managing those resources and more time focusing on your applications that run in AWS. You create a template that describes all the AWS resources that you want (like Amazon EC2 instances or Amazon RDS DB instances), and AWS CloudFormation takes care of provisioning and configuring those resources for you. You don't need to individually create and configure AWS resources and figure out what's dependent on what; AWS CloudFormation handles all of that.; Option A is not correct. Amazon Inspector is an automated security assessment service that helps improve the security and compliance of applications deployed on AWS.; Option B is not correct. AWS Config is a service that enables you to assess, audit, and evaluate the configurations of your AWS resources.; Option D is not correct. Amazon EMR is used to run and scale Apache Spark, Hadoop, HBase, Presto, Hive, and other Big Data Frameworks.; References:; https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/Welcome.html

Amazon Route 53 provides highly available and scalable Domain Name System (DNS) services, domain name registration, and health-checking web services. It is designed to give developers and businesses an extremely reliable and cost effective way to route end users to Internet applications by translating names like example.com into the numeric IP addresses, such as 192.0.2.1, that computers use to connect to each other.; Option B is not correct. Amazon VPC allows you to create a virtual network in the cloud.; Option C is not correct. AWS Direct Connect is a cloud service solution that is used to establish a dedicated network connection from your premises to AWS.; Option D is not correct. AWS Virtual Private Network (AWS VPN) is used to establish a secure and private tunnel from your network or device to the AWS global network.; References:; https://aws.amazon.com/route53/

The Amazon Elastic MapReduce and DynamoDB are managed services that you don’t need to manage their underlying infrastructure. Other managed services include: Amazon S3, Amazon RDS, Amazon Redshift, Amazon WorkSpaces, Amazon CloudFront, Amazon CloudSearch and several other services.; Option B is not correct. Amazon EC2 is a service that gives you complete control over your compute resources. You are responsible for managing almost everything in your server instances when using Amazon EC2.; Option D is not correct. Amazon Virtual Private Cloud (Amazon VPC) lets you provision a logically isolated section of the AWS Cloud where you can launch AWS resources in a virtual network that you define. You have complete control over your virtual networking environment. Amazon VPC is not a managed service, you are responsible for managing almost everything when using the Amazon VPC service.; References:; https://aws.amazon.com/dynamodb/;   https://aws.amazon.com/emr/

Amazon S3 is an object level storage built to store and retrieve any amount of data from anywhere – web sites and mobile apps, corporate applications, and data from IoT sensors or devices. It is designed to deliver 99.999999999% durability, and stores data for millions of applications used by market leaders in every industry.; Option A is not correct. Amazon EBS is a block level storage technology.; Option C is not correct. AWS Storage Gateway is a hybrid storage service that enables your on-premises applications to seamlessly use AWS cloud storage. The gateway connects to AWS storage services - such as Amazon S3 (which is object level) and Amazon EBS (which is block level) - and provides storage for files, volumes, snapshots, and virtual tapes in AWS.; Option D is not correct. Amazon SQS is not a storage service. It is a message queue service that enables you to decouple microservices, distributed systems, and serverless applications.; References:; https://aws.amazon.com/s3/

The AWS Global infrastructure is built around Regions and Availability Zones (AZs). Each AWS Region is a separate geographic area. Each AWS Region has multiple, isolated locations known as Availability Zones. Availability Zones in a region are connected with low latency, high throughput, and highly redundant networking. These Availability Zones offer AWS customers an easier and more effective way to design and operate applications and databases, making them more highly available, fault tolerant, and scalable than traditional single datacenter infrastructures or multi-datacenter infrastructures.; In addition to replicating applications and data across multiple data centers in the same Region using Availability Zones, you can also choose to increase redundancy and fault tolerance further by replicating data between geographic Regions (especially if you are serving customers from all over the world). You can do so using both private, high speed networking and public internet connections to provide an additional layer of business continuity, or to provide low latency access across the globe.; Option A is not correct. VPC refers to the virtual private cloud which is a virtual network that you define. Deploying the application across multiple VPC’s in the same region will not help your global customers. This option can only be true if the VPCs are created in multiple regions worldwide.; Option C is not correct. Edge locations are not used to host applications. Edge locations are used by CloudFront to cache and distribute content to your global customers with low latency.; Option D is not correct. A subnet is a range of IP addresses in your VPC.; References:; https://aws.amazon.com/about-aws/global-infrastructure/

AWS Database Migration Service (DMS) helps you migrate databases to AWS easily and securely. The source database remains fully operational during the migration, minimizing downtime to applications that rely on the database. The AWS Database Migration Service can migrate your data to and from most widely used commercial and open-source databases. The service supports homogeneous migrations such as Oracle to Oracle, as well as heterogeneous migrations between different database platforms, such as Oracle to Amazon Aurora or Microsoft SQL Server to MySQL. It also allows you to stream data to Amazon Redshift from any of the supported sources including Amazon Aurora, PostgreSQL, MySQL, MariaDB, Oracle, SAP ASE, and SQL Server, enabling consolidation and easy analysis of data in the petabyte-scale data warehouse. AWS Database Migration Service can also be used for continuous data replication with high availability.   ; Option A is not correct. RDS Multi-AZ is a feature of Amazon RDS that is used to increase the availability of the database.; Option B is not correct. AWS Server Migration Service (SMS) is used to migrate your on-premises workloads to AWS.; Option C is not correct. AWS Application Discovery Service helps enterprise customers plan migration projects by gathering information about their on-premises data centers.; References: ; https://d1.awsstatic.com/whitepapers/aws-overview.pdf

With On-Demand instances, you pay for compute capacity by the hour with no long-term commitments. You can increase or decrease your compute capacity depending on the demands of your application and only pay the specified hourly rate for the instances you use. The use of On-Demand instances frees you from the costs and complexities of planning, purchasing, and maintaining hardware and transforms what are commonly large fixed costs into much smaller variable costs. On-Demand instances also remove the need to buy “safety net” capacity to handle periodic traffic spikes.; Option A is not correct. Reserved instances are not appropriate in this case because you have to purchase capacity for at least one year.; Option B is not correct. Spot is not a good choice as the application must run without interruption.; Option C is not correct. Dedicated instances can be used if you require your instance be physically isolated at the host hardware level from instances that belong to other AWS accounts.; References: ; https://d1.awsstatic.com/whitepapers/aws-overview.pdf

Security groups are used to define and control the way you want your instances to be accessed, and whether or not certain kind of communications is allowed. AWS security groups provide security at the protocol and port access level. You can add rules to each security group that allow traffic to or from its associated instances.; Option A is not correct. DB security groups are used to control access to the databases.; Option B is not correct.IAM policies are used to grant users permissions to perform specific actions on EC2. A user can only access the instance and perform these actions if his IP address is allowed in the security group that is attached to the instance. In brief, security groups are used to control who can access the instance. IAM policies are used to control what actions can a specific user perform after accessing the instance.; References:; https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/UsingIAM.html; https://docs.aws.amazon.com/vpc/latest/userguide/VPC_SecurityGroups.html

There are three Cloud Computing Models: ; 1) Infrastructure as a Service (IaaS) - Infrastructure as a Service (IaaS) contains the basic building blocks for cloud IT and typically provide access to networking features, computers (virtual or on dedicated hardware), and data storage space. IaaS provides you with the highest level of flexibility and management control over your IT resources and is most similar to existing IT resources that many IT departments and developers are familiar with today.   ; 2) Platform as a Service (PaaS) - Platform as a Service (PaaS) removes the need for your organization to manage the underlying infrastructure (usually hardware and operating systems) and allows you to focus on the deployment and management of your applications. This helps you be more efficient as you don’t need to worry about resource procurement, capacity planning, software maintenance, patching, or any of the other undifferentiated heavy lifting involved in running your application.   ; 3) Software as a Service (SaaS) - Software as a Service (SaaS) provides you with a completed product that is run and managed by the service provider. In most cases, people referring to Software as a Service are referring to end-user applications. With a SaaS offering you do not have to think about how the service is maintained or how the underlying infrastructure is managed; you only need to think about how you will use that particular piece of software. A common example of a SaaS application is web-based email which you can use to send and receive email without having to manage feature additions to the email product or maintain the servers and operating systems that the email program is running on. ; References: ; https://docs.aws.amazon.com/aws-technical-content/latest/aws-overview/types-of-cloud-computing.html

Amazon CloudWatch is a service that monitors AWS cloud resources and the applications you run on AWS. You can use Amazon CloudWatch to collect and track metrics, collect and monitor log files, set alarms, and automatically react to changes in your AWS resources. Amazon CloudWatch can monitor AWS resources such as Amazon EC2 instances, Amazon DynamoDB tables, and Amazon RDS DB instances, as well as custom metrics generated by your applications and services, and any log files your applications generate.; Option A is not correct. AWS Config is a service that enables you to assess, audit, and evaluate the configurations of your AWS resources.; Option B is not correct. Amazon Inspector is an automated security assessment service that helps improve the security and compliance of applications deployed on AWS.; Option D is not correct. AWS Trusted Advisor is an online tool that provides real time guidance to help you provision your resources following AWS best practices.; References:; https://aws.amazon.com/cloudwatch/

Option A :; ** All of the physical security are taken care of for you. Amazon data centers are surrounded by three physical layers of security. “Nothing can go in or out without setting off an alarm”. It’s important to keep bad guys out, but equally important to keep the data in which is why Amazon monitors incoming gear, tracking every disk that enters the facility. And “if it breaks we don’t return the disk for warranty. The only way a disk leaves our data center is when it’s confetti.”; ** Most (not all) data and network security are taken care of for you. When we talk about the data/network security, AWS has a “shared responsibility model” where AWS and the customer share the responsibility of securing them. For example the customer is responsible for creating rules to secure his network traffic using the security groups and is also responsible for protecting data with encryption.; Option C:; In a cloud computing environment, new IT resources are only a click away, which means it requires less time to make those resources available to developers - from weeks to just minutes. This results in a dramatic increase in agility for the organization, since the cost and time it takes to experiment and develop is significantly lower.; Option B is not correct. The Physical infrastructure is a responsibility of AWS and not the customer. Hence it is not an advantage of moving to the AWS Cloud.; Option D is not correct. In AWS, most of the services are available with no upfront costs as it follows the pay-as-you-go pricing.; AWS allows you to pay upfront for some services to get more discounts, but you have the choice to pay upfront or pay as you go. By contrast, traditional IT providers require you to pay upfront for all of their services.; Option E is not correct. As mentioned above, security is a shared responsibility between AWS and the customer. For example, the customer has to manage who can access and use AWS resources using the IAM service.; References:; https://docs.aws.amazon.com/aws-technical-content/latest/aws-overview/six-advantages-of-cloud-computing.html