AWS Certified Solutions Architect Associate (SAA02) – Free Practice Tests

Explanation

A placement group is a logical grouping of instances within a single Availability Zone. Cluster placement groups are recommended for applications that benefit from low network latency, high network throughput, or both. To provide the lowest latency, and the highest packet-per-second network performance for your cluster placement group, choose an instance type that supports enhanced networking

Explanation

The user cannot authorize an Amazon EC2 security group if it is in a different AWS Region than the RDS DB instance. The user can authorize an IP range or specify an Amazon EC2 security group in the same region that refers to an IP address in another region. In this case allow IP of US West inside US East’s security group and open the RDS security group for US East region.

Explanation

FGAC can benefit any application that tracks information in a DynamoDB table, where the end user (or application client acting on behalf of an end user) wants to read or modify the table directly, without a middle-tier service. For instance, a developer of a mobile app named Acme can use FGAC to track the top score of every Acme user in a DynamoDB table. FGAC allows the application client to modify only the top score for the user that is currently running the application

Explanation

You can use geo restriction, also known as geoblocking, to prevent users in specific geographic locations from accessing content that you’re distributing through a CloudFront web distribution.

To use geo restriction, you have two options:

Explanation

Amazon Simple Queue Service (SQS) is a fast, reliable, scalable, and fully managed message queuing service. SQS provides a simple and cost-effective way to decouple the components of an application. The user can configure SQS, which will decouple the call between the EC2 application and S3. Thus, the application does not keep waiting for S3 to provide the data.

Explanation

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. A template is a JSON-formatted text file that describes your AWS infrastructure. Templates include several major sections. The Resources section is the only section that is required. The first character in the template must be an open brace ({), and the last character must be a closed brace (}). The following template fragment shows the template structure and sections

Explanation

The organization can always launch multiple EC2 instances in the same region across multiple availability zones for high availability and disaster recovery. It is recommended that the application should be load balanced for better load distribution. When the organization must support a workload that could be met with a small number of large instances, it is recommended to distribute the load by creating four small instances across availability zones. The two large instances give only 50% redundancy while the four small instances give 75% redundancy. As for cost, both the scenarios are the same it is recommended to run four small instances across availability zones

Explanation

The conditions section of a CloudFormation template defines conditions that control whether certain resources are created or whether certain resource properties are assigned a value during stack creation or update. For example, you could conditionally create a resource that depends on whether the stack is for a production or test environment

Explanation

Amazon Simple Queue Service (SQS) is a highly reliable distributed messaging system for storing messages as they travel between computers. By using Amazon SQS, developers can simply move data between distributed application components. It is used to achieve compartmentalization or loose coupling. In this case all the modules will send a message to the logger queue and the data will be processed by queue as per the resource availability.

Explanation

There are essentially three types of answers here – choices that use no automation, choices that use the incorrect type of automation given the situation, and a choice that uses the correct type of automation.

First, the choices that use little to no automation in this case would be the least recommended decision. Uploading millions of files to either Standard or Standard-IA and then waiting to review costs and access patterns could be very costly.

Second, the choice to use storage class analysis could work eventually, if you have the time to wait for analytics to be gathered (which could still be as costly as the choice above) and the time to then review the analytics, and then sift through the files to migrate them to the correct storage class. This is a better choice, but not the best choice.

Finally, the correct answer would be to use Intelligent_Tiering, which continuously monitors the access frequency and shifts the objects between a standard and infrequent-access tier depending on how access patterns may change. This happens automatically, and starts immediately, so it is the best choice of the options provided.

Explanation

By default, a target starts to receive its full share of requests as soon as it is registered with a target group and passes an initial health check. Using slow start mode gives targets time to warm up before the load balancer sends them a full share of requests.

Increasing the maximum threshold for your auto scaling group will allow you to process more requests.

Explanation

For an EC2 instance launched with an EBS backed Windows AMI, each time the instance state is changed from stop to start/ running, AWS charges restart a new per-hour charge. Effective October 2, 2017, charges are calculated on a per-second basis for On-Demand, Spot and Reserved instances with Linux operating systems, with a minimum one-minute charge. Regardless of operating system, rebooting an instance AWS does not incur a charge an hour or one-minute minimum charge.

Explanation

Explanation

Amazon Kinesis is a fully managed service for real-time processing of streaming data at massive scale. Amazon Kinesis can continuously capture and store terabytes of data per hour from hundreds of thousands of sources such as website clickstreams, financial transactions, social media feeds, IT logs, and location-tracking events. With Amazon Kinesis Client Library (KCL), you can build Amazon Kinesis Applications and use streaming data to power real-time dashboards, generate alerts, implement dynamic pricing and advertising, and more.

Explanation

A cluster placement group is a logical grouping of instances within a single AWS Availability Zone. Placement groups are recommended for applications that benefit from low network latency, high network throughput, or both. To provide the lowest latency, and the highest packet-per-second network performance for your placement group, choose an instance type that supports enhanced networking.

Explanation

T2 instances are Burstable Performance Instances that provide a baseline level of CPU performance with the ability to burst above the baseline. The baseline performance and ability to burst are governed by CPU Credits. M4 instances are the latest generation of General Purpose Instances. This family provides a balance of compute, memory, and network resources, and it is a good choice for many applications. In this instance, the only option which provides for growth while keeping costs in check is to upgrade to reserved M4 instances on a long term 3 year contract.

Explanation

Each Amazon S3 bucket and object has an ACL (Access Control List) associated with it. An ACL is a list of grants identifying the grantee and the permission granted. The user can use ACLs to grant basic read/write permissions to other AWS accounts. ACLs use an Amazon S3–specific XML schema. The user cannot grant permissions to other users in his account. ACLs are suitable for specific scenarios. For example, if a bucket owner allows other AWS accounts to upload objects, permissions to these objects can only be managed using the object ACL by the AWS account that owns the object

Explanation

Amazon EC2 allows the user to launch On-Demand instances. Auto Scaling offers automation which can scale up or down resources as per the configured policy.

To set up Auto Scaling, the organization must first create an AMI. The organization should set up bootstrapping for the AMI so that when the instance is launched, it will automatically start the app server and DB server.

The organization should also setup ELB with instances to distribute the incoming load. Auto Scaling should be configured to scale up and down based on the application load and not on a particular schedule.

Explanation

Cost Explorer, this is a useful and powerful tool within Billing and Cost Management. It allows you to view historical billing information in a graphical format giving you greater insight to your AWS spend. A valuable tool that can help to identify where you should be focusing your cost optimization efforts. It also can forecast your estimated spend up to two months ahead using existing data as a reference. If you can see that your estimated future bills are becoming too high, you have the time now to identify where you can make and initiate cost reduction mechanisms to help mitigate the risk.

Cost Explorer comes configured with three pre-defined views which are commonly used to analyze spending across your account:

1. Monthly Spend by Service view – this covers the current and previous two months and is grouped by AWS services
2. Monthly Spend by Linked Account View – this covers the current and previous two months and is grouped by linked accounts
3. Daily Spend view – this covers the daily spend over the previous sixty days

Explanation

Amazon Elastic Compute Cloud (Amazon EC2) provides scalable computing capacity in the Amazon Web Services (AWS) cloud. Using Amazon EC2 eliminates your need to invest in hardware up front, so you can develop and deploy applications faster. You can use Amazon EC2 to launch as many or as few virtual servers as you need, configure security and networking, and manage storage. Amazon EC2 enables you to scale up or down to handle changes in requirements or spikes in popularity, reducing your need to forecast traffic

Explanation

On-premises data centers have costs associated with the servers, storage, networking, power, cooling, physical space, and IT labor required to support applications and services running in the production environment. For servers, these questions are most applicable: What is your average server utilization? How much do you overprovision for peak load? What is the cost of over-provisioning?

Explanation

You can use snapshots to increase the size of EBS volumes. Take a snapshot of the existing volume, create a new volume from the snapshot but with a larger size, then replace the original snapshot with the new volume. There is a performance hit with new volumes because, while the volume is created immediately, the data is lazy loaded. So there will be a first time performance hit when accessing each block on the volume. This problem can be resolved by initializing the volume and accessing each block one time before the volume is put into service.

Explanation

The pricing of SQS is as follows: You pay only for what you use, and there is no minimum fee. The cost of Amazon SQS is calculated per request, plus data transfer charges for data transferred out of Amazon SQS. The Amazon SQS Free Tier provides you with 1 million requests per month at no charge. Many small-scale applications are able to operate entirely within the limits of the Free Tier. However, data transfer charges might still apply.

Explanation

If you get an InsufficientInstanceCapacity error when you try to launch an instance or start a stopped instance, AWS does not currently have enough available capacity to service your request. In this situation, reserved instances offer the required reliability to avoid outages and loss of money. Reserved Instances are a long-term capacity reservation, and you will not have to rely on Amazon having enough on-demand capacity. Usually these capacity issues are short term, but due to the nature of the company even short outages can be very costly.

Explanation

A security group acts as a virtual firewall for your instance to control inbound and outbound traffic. When you launch an instance in a VPC, you can assign the instance to up to five security groups. Security groups act at the instance level, not the subnet level. Therefore, each instance in a subnet in your VPC could be assigned to a different set of security groups. If you don’t specify a particular group at launch time, the instance is automatically assigned to the default security group for the VPC. If an instance is running in an Amazon VPC you can change which security groups are associated with an instance while the instance is running.

Explanation

Trusted Advisor checks for Amazon EC2 reserved instances optimization, low utilization of Amazon EC2 instances, idle Load Balancers, underutilized Amazon EBS Volumes, unassociated Elastic IP Addresses, Amazon RDS idle DB instances, Amazon Route 53 Latency Resource Record Sets, Amazon EC2 reserved instance lease expiration and underutilized Amazon Redshift Clusters

Explanation

Check the network access control list (ACL) for the subnet. The network ACLs must allow inbound and outbound traffic from your local IP address on the proper port. The default network ACL allows all inbound and outbound traffic. To enable Internet access for the EC2 instances in a VPC, you must create an Internet Gateway as well as a route to it in the router table.

Explanation

Amazon S3 supports several mechanisms that give you flexibility to control who can access your data as well as how, when, and where they can access it. Amazon S3 provides four different access control mechanisms: AWS Identity and Access Management (IAM) policies, Access Control Lists (ACLs), bucket policies, and query string authentication. IAM enables organizationsto create and manage multiple users under a single AWS account. With IAM policies, you can grant IAM users fine-grained control to your Amazon S3 bucket or objects. You can use ACLs to selectively add (grant) certain permissions on individual objects. Amazon S3 bucket policies can be used to add or deny permissions across some or all of the objects within a single bucket. With Query string authentication, you have the ability to share Amazon S3 objects through URLs that are valid for a specified period of time.

Explanation

A placement group is a logical grouping of instances within a single Availability Zone. Cluster placement groups are recommended for applications that benefit from low network latency, high network throughput, or both. To provide the lowest latency, and the highest packet-per-second network performance for your cluster placement group, choose an instance type that supports enhanced networking

Explanation

Amazon S3 Glacier Deep Archive storage class is the cheapest storage class in AWS, and the information can be retrieved within 12 hours.

The other options offer some cost savings compared to Amazon S3 Standard storage class, but Intelligent tiering would not cycle the files to an archive storage class for roughly 120 days, and the One Zone-IA storage class would provide some cost savings, but offers less durable storage, so the likelihood of losing logs is higher.

Explanation

You can write an AWS CloudFormation template (a JSON-formatted document) in a text editor or pick an existing template. The template describes the resources you want and their settings. For example, suppose you want to create an Amazon EC2. Your template can declare an instance Amazon EC2 and describe its properties

Explanation

In the event of a disaster to your AWS infrastructure you should be able to quickly launch resources in Amazon Web Services (AWS) to ensure business continuity. The following are some key steps you should have in place for preparation: 1. Set up Amazon EC2 instances to replicate or mirror data. 2. Ensure that you have all supporting custom software packages available in AWS. 3. Create and maintain AMIs of key servers where fast recovery is required. 4. Regularly run these servers, test them, and apply any software updates and configuration changes. 5. Consider automating the provisioning of AWS resources.

Explanation

Amazon Redshift is a fast, fully managed data warehouse that makes it simple and cost-effective to analyze all your data using standard SQL and your existing Business Intelligence (BI) tools. It allows you to run complex analytic queries against petabytes of structured data, using sophisticated query optimization, columnar storage on high-performance local disks, and massively parallel query execution.

Explanation

As your needs change, you might find that your instance is over-utilized (the instance type is too small) or under-utilized (the instance type is too large). If the root device for your instance is an Elastic Block Store (EBS) volume, you can change the size of the instance simply by changing its instance type, which is known as resizing it. If the root device for your instance is an instance store volume, you must migrate your application to a new instance with the instance type that you want

Explanation

Regarding Amazon Route 53, if your application is running on Amazon EC2 instances in two or more regions, and if you have more than one Amazon EC2 instance in one or more regions, you can use latency-based routing to route traffic to the correct region and then use weighted resource record sets to route traffic to instances within the region based on weights that you specify

Explanation

In AWS CloudFormation, Amazon EC2 resources that support the tagging feature can also be tagged in an AWS template. The tag values can refer to template parameters, other resource names, resource attribute values (e.g. addresses), or values computed by simple functions (e.g., a concatenated list of strings).

Explanation

Amazon EC2 allows the user to launch On-Demand instances. Auto Scaling offers automation which can scale up or down resources as per the configured policy.

To set up Auto Scaling, the organization must first create an AMI. The organization should set up bootstrapping for the AMI so that when the instance is launched, it will automatically start the app server and DB server.

The organization should also setup ELB with instances to distribute the incoming load. Auto Scaling should be configured to scale up and down based on the application load and not on a particular schedule.

Explanation

Amazon RDS provides three storage types: magnetic, General Purpose (SSD), and Provisioned IOPS (input/output operations per second). They differ in performance characteristics and price, allowing you to tailor your storage performance and cost to the needs of your database workload. General purpose is good for small to medium sized databases and has the burst to handle spikes.

Explanation

EC2 instance store volumes can be added as additional volumes to certain EBS-backed EC2 Instance types. Any data on the instance store volumes persists as long as the instance is running, but this data is deleted when the instance is terminated or if it fails (such as if an underlying drive has issues).

Explanation

By default, a target starts to receive its full share of requests as soon as it is registered with a target group and passes an initial health check. Using slow start mode gives targets time to warm up before the load balancer sends them a full share of requests.

Increasing the maximum threshold for your auto scaling group will allow you to process more requests.

Explanation

You can set up a variety of failover configurations using Amazon Route 53 alias: weighted, latency, geolocation routing, and failover resource record sets. Active-active failover: Use this failover configuration when you want all of your resources to be available the majority of the time. When a resource becomes unavailable, Amazon Route 53 can detect that it’s unhealthy and stop including it when responding to queries. Active-passive failover: Use this failover configuration when you want a primary group of resources to be available the majority of the time and you want a secondary group of resources to be on standby in case all of the primary resources become unavailable. When responding to queries, Amazon Route 53 includes only the healthy primary resources. If allof the primary resources are unhealthy, Amazon Route 53 begins to include only the healthy secondary resources in response to DNS queries. Active-active-passive and other mixed configurations: You can combine alias and non-alias resource record sets to produce a variety of Amazon Route 53 behaviors.

Explanation

Uploading data to the Snowball Appliance requires a client application. The upload is CPU, memory, and networking intensive. If you are uploading large amounts of data, Amazon recommends that you run the client software on multiple workstations to distribute the load and thereby shorten the time the upload will take.

Explanation

After you turn on S3 Transfer Acceleration for a bucket, two new endpoints are created for the bucket: one for IPv4 and one for IPv6. You can use either the accelerate endpoints or the standard endpoints if you choose not to use the accelerate feature.

Explanation

Amazon EBS provides three volume types: General Purpose SSD, Provisioned IOPS SSD, and Magnetic.

General Purpose SSD volumes are the default EBS volume type for Amazon EC2 instances.

GP2 volumes smaller than 1 TB can burst up to 3,000 IOPS. I/O is included in the price of gp2, so you pay only for each GB of storage you provision. GP2 is designed to deliver the provisioned performance 99% of the time. If you need a greater number of IOPS than gp2 can provide, or if you have a workload where low latency is critical or you need better performance consistency, we recommend that you use io1.

Explanation

Application Load Balancer
You are charged for each hour or partial hour that an Application Load Balancer is running and the number of Load Balancer Capacity Units (LCU) used per hour.

Network Load Balancer
You are charged for each hour or partial hour that a Network Load Balancer is running and the number of Load Balancer Capacity Units (LCU) used by Network Load Balancer per hour.

Classic Load Balancer
You are charged for each hour or partial hour that a Classic Load Balancer is running and for each GB of data transferred through your load balancer.

Explanation

Amazon RDS provides high availability and failover support for DB instances using Multi-AZ deployments. Amazon RDS uses several different technologies to provide failover support. Multi-AZ deployments for Oracle, PostgreSQL, MySQL, and MariaDB DB instances use Amazon’s failover technology. SQL Server DB instances use SQL Server Mirroring. Amazon Aurora instances stores copies of the data in a DB cluster across multiple Availability Zones in a single region, regardless of whether the instances in the DB cluster span multiple Availability Zones.

Explanation

Don’t use your AWS root account credentials to access AWS, and don’t give your credentials to anyone else. Instead, create individual users for anyone who needs access to your AWS account. Create an IAM user for yourself as well, give that user administrative privileges, and use that IAM user for all your work.

Explanation

In AWS, the instance size decides the I/O characteristics. The provisioned IOPS ensures higher throughput, and lower latency. The region does affect the latency, latency will always be less when the instance is near to the end user. Within a region the user uses any AZ and this does not affect the latency. The AZ is mainly for fault toleration or HA

Explanation

Elastic Beanstalk environments can be changed after creation. For example, if you have a compute-intensive application, you can change the type of Amazon EC2 instance that is running your application. To do this, you use the Scaling option in the management page of the Elastic Beanstalk console and change the minimum instance count.

Explanation

You can use geo restriction, also known as geoblocking, to prevent users in specific geographic locations from accessing content that you’re distributing through a CloudFront web distribution.

To use geo restriction, you have two options:

Explanation

If your database workload requires more I/O than you have provisioned, recovery after a failover or database failure will be slow. To increase the I/O capacity of a DB instance, do any or all of the following:

Explanation

Amazon S3 is storage for the Internet. It’s a simple storage service that offers software developers a highly-scalable, reliable, and low-latency data storage infrastructure at very low costs. AWS charges less where their costs are less. For example, their costs are lower in the US Standard Region than in the US West (Northern California) Region.

Explanation

Dynamic scaling can provide a very robust scaling option. But it is not the only option and not always the best option in all scenarios. Manual scaling and scheduled scaling also have use cases where they may be a better choice than dynamic scaling. Increasing resources to improve performance is certainly the most common use case for scaling. However, it is important also to be aware of the effects of scaling on cost. Utilizing auto scaling in conjunction with Cloudwatch monitoring can help insure that resources are scaled in and out appropriately and that money is not wasted on idle or underused resources

Explanation

Cost Explorer, this is a useful and powerful tool within Billing and Cost Management. It allows you to view historical billing information in a graphical format giving you greater insight to your AWS spend. A valuable tool that can help to identify where you should be focusing your cost optimization efforts. It also can forecast your estimated spend up to two months ahead using existing data as a reference. If you can see that your estimated future bills are becoming too high, you have the time now to identify where you can make and initiate cost reduction mechanisms to help mitigate the risk.

Cost Explorer comes configured with three pre-defined views which are commonly used to analyze spending across your account:

1. Monthly Spend by Service view – this covers the current and previous two months and is grouped by AWS services
2. Monthly Spend by Linked Account View – this covers the current and previous two months and is grouped by linked accounts
3. Daily Spend view – this covers the daily spend over the previous sixty days

Explanation

When you want to include instances with multiple purchase types in the same auto scaling group, you have the ability to maintain a set number of on-demand instances will be deployed at all times, and then split the remaining instances between multiple purchase types as you see fit. To configure this, set a number of instances as your “optional on-demand base” within your launch template. This is not possible using a launch configuration.

Explanation

To enable access to or from the Internet for instances in a VPC subnet, you must do the following:

Explanation

To prevent the public DNS address for your instance from changing and breaking your installation, you can associate an Elastic IP address (EIP) to the instance you are using. You need to allocate an Elastic IP address for that instance (the first association is free). If you own a domain name and you want to use it for your blog, you can update the DNS record for the domain name to point to your EIP address. If you don’t already have a domain name for your blog, you can register a domain name with Amazon Route 53 and associate your instance’s EIP address with your domain name.

Explanation

Multipart uploads must be used for files greater than 5 GB. Cross-region replication is used to reduce latency by placing objects closer to users. This would address the issue of having users in different continents. Another use case for cross-region replication is to meet compliance requirements of storing backup data a certain distance from their origin.

Explanation

The CORS specification gives a user the ability to build web applications that make requests to domains other than the one which supplied the primary content. The ACLs and policies continue to apply when you enable CORS on the bucket.

Explanation

By default, when you purchase a Reserved Instance, it is executed immediately. Alternatively, you can queue your purchases for a future date and time. For example, you can queue a purchase for around the time that an existing Reserved Instance expires. This can help you ensure that you have uninterrupted coverage.

You can queue purchases for regional Reserved Instances, but not zonal Reserved Instances or Reserved Instances from other sellers. You can queue a purchase up to three years in advance. On the scheduled date and time, the purchase is executed using the default payment method. After the payment is successful, the billing benefit is applied.

Explanation

AWS is responsible for the security of the cloud in general, in areas such data security and protection against IP spoofing. The customer is responsible for security in the cloud in areas such as data encryption, installing security patches on EC2 instances, and IAM best practices. It is very important to understand this concept to avoid any lapses in your security measures.

Explanation

Each CloudWatch alarm watches a single metric and sends messages to Auto Scaling when the metric breaches a threshold that you specify in your policy. Changing the scale down the CloudWatch metric to a higher threshold will not cost any more.

Auto Scaling also supports adding life-cycle hooks to Auto Scaling groups. These hooks enable you to control how instances launch and terminate within an Auto Scaling group; you can perform actions on the instance before it is put into service or before it is terminated. This is also cost-efficient and hence also a correct answer.

All the other answers will not optimize costs.

Explanation

Amazon Redshift applies changes to a cluster security group immediately. So if you have associated the cluster security group with a cluster, inbound cluster access rules in the updated cluster security group apply immediately.

Explanation

If an EBS volume is attached to a running EC2 instance, the user needs to detach the volume from the original instance and then attach it to a new running instance. The user doesn’t need to stop or terminate the original instance.

Explanation

Blue/green deployments resolve application unavailability during updates.

Explanation

All traffic should be routed via Internet Gateway. So, a route should be created with 0.0.0.0/0 as a source, and your Internet Gateway as your target.

Explanation

An instance store provides temporary block-level storage for your instance. This storage is located on disks that are physically attached to the host computer. Instance store is ideal for temporary storage of information that changes frequently, such as buffers, caches, scratch data, and other temporary content, or for data that is replicated across a fleet of instances, such as a load-balanced pool of web servers.

Data in the instance store is lost under the following circumstances:

• The underlying disk drive fails
• The instance stops
• The instance terminates

If the instance reboots (either intentionally or unintentionally) the data persists.

Explanation

On-premises data centers have costs associated with the servers, storage, networking, power, cooling, physical space, and IT labor required to support applications and services running in the production environment. For servers, these questions are most applicable: What is your average server utilization? How much do you overprovision for peak load? What is the cost of over-provisioning?

Explanation

With target tracking scaling policies, you select a scaling metric and set a target value. Amazon EC2 Auto Scaling creates and manages the CloudWatch alarms that trigger the scaling policy and calculates the scaling adjustment based on the metric and the target value. The scaling policy adds or removes capacity as required to keep the metric at, or close to, the specified target value. In addition to keeping the metric close to the target value, a target tracking scaling policy also adjusts to the changes in the metric due to a changing load pattern.

Explanation

You can create a VPC with an instance tenancy of dedicated to ensure that all instances launched into the VPC are dedicated instances. Alternatively, you can specify the tenancy of the instance during launch

Explanation

Creating separate VPC Peering connections between each VPC is required for Peering 3 VPCs together. Transitive routing is not supported in VPC Peering so VPC C could not reach VPC A through VPC B. A new VPC Peering connection is required for connecting additional VPCs, so connecting VPC A to pcx-abcxyz is not a viable option. Adding a static route to VPC A that points to pcx-abcxyz would not work as pcx-abcxyz is not connected to VPC A.

Explanation

You can place a network interface on each of your web servers that connects to a mid-tier network where an application server resides. The application server can also be dual-homed to a back-end network (subnet) where the database server resides. Instead of routing network packets through the dual-homed instances, each dual-homed instance receives and processes requests on the front end, initiates a connection to the back end, and then sends requests to the servers on the back-end network.

Explanation

A security group controls the access to a DB instance. It does so by allowing access to IP address ranges or Amazon EC2 instances that you specify. Amazon RDS uses DB security groups, VPC security groups, and EC2 security groups. In simple terms, a DB security group controls access to a DB instance that is not in a VPC, a VPC security group controls access to a DB instance inside a VPC, and an Amazon EC2 security group controls access to an EC2 instance and can be used with a DB instance.