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

Explanation

In AWS EC2, while configuring a security group, the user needs to specify the IP address in CIDR notation. The CIDR IP range 10.20.30.40/32 says it is for a single IP 10.20.30.40. If the user specifies the IP as 10.20.30.40 only, the security group will not accept and ask it in a CIDR format

Explanation

The ability to pause multipart uploads offers great flexibility in its usage. A pause could be initiated for a number of reasons but pausing to relieve network traffic is a prime use case. If a multipart upload aborts, it is good practice to have a lifecycle policy, which will delete incomplete uploads after a predetermined number of days. This will reduce storage costs.

Explanation

An Elastic Load Balancer(ELB) by default, routes each request independently to the application instance with the smallest load. However, you can use the sticky session feature (also known as session affinity), which enables the load balancer to bind a user’s session to a specific application instance. This ensures that all requests coming from the user during the session will be sent to the same application instance. The key to managing the sticky session is determining how long your load balancer should consistently route the user’s request to the same application instance. If your application has its own session cookie, then you can set Elastic Load Balancing to create the session cookie to follow the duration specified by the application’s session cookie. If your application does not have its own session cookie, then you can set Elastic Load Balancing to create a session cookie by specifying your own stickiness duration. You can associate stickiness duration for only HTTP/HTTPS load balancer listeners. An application instance must always receive and send two cookies: A cookie that defines the stickiness duration and a special Elastic Load Balancing cookie named AWSELB, that has the mapping to the application instance.

Explanation

The method that you use to edit a service-linked role depends on the service. Some services might allow you to edit the permissions for a service-linked role from the service console, API, or CLI. However, after you create a service-linked role, you cannot change the name of the role because various entities might reference the role. You can edit the description of any role from the IAM console, API, or CLI.

For information about which services support using service-linked roles, see AWS Services That Work with IAM and look for the services that have Yes in the Service-Linked Role column. To learn whether the service supports editing the service-linked role, choose the Yes link to view the service-linked role documentation for that service.

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

When you create a default VPC, the following components are created with it:

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

Security Groups are essentially stateful firewalls at the instance level. Security Groups are associated with instances at launch time, and restrict or allow traffic based on port, protocol, and source/destination.

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

If you have multiple VPN connections, you can provide secure communication between sites using the AWS VPN CloudHub. The VPN CloudHub operates on a simple hub-and-spoke model that you can use with or without a VPC. This design is suitable for customers with multiple branch offices and existing Internet connections who’d like to implement a convenient, potentially low-cost hub-and-spoke model for primary or backup connectivity between these remote offices. To use the AWS VPN CloudHub, you must create a virtual private gateway with multiple customer gateways, each with unique Border Gateway Protocol (BGP) Autonomous System Numbers (ASNs). Customer gateways advertise the appropriate routes (BGP prefixes) over their VPN connections. These routing advertisements are received and re-advertised to each BGP peer, enabling each site to send data to and receive data from the other sites. The routes for each spoke must have unique ASNs and the sites must not have overlapping IP ranges. Each site can also send and receive data from the VPC as if they were using a standard VPN connection

Explanation

Amazon EC2 supports the following storage options: Amazon Elastic Block Store (Amazon EBS) Amazon EC2 Instance Store Amazon Simple Storage Service (Amazon S3) Reference:

Explanation

You can secure your VPC instances using only security groups; however, you can add NACLs as a second layer of defense. Security groups — Act as a firewall for associated Amazon EC2 instances, controlling both inbound and outbound traffic at the instance level .  Network access control lists (NACLs) — Act as a firewall for associated subnets, controlling both inbound and outbound traffic at the subnet level . Security Groups supports allow rules only while Network Access Control Lists support allow and deny rules.

Explanation

Amazon SQS is a distributed queuing system that is optimized for horizontal scalability, not for single-threaded sending or receiving speeds. A single client can send or receive Amazon SQS messages at a rate of about 5 to 50 messages per second. Higher receive performance can be achieved by requesting multiple messages (up to 10) in a single call. It may take several seconds before a message that has been to a queue is available to be received.

Explanation

OpsWorks stacks will let you utilize your existing Chef recipes, but only OpsWorks for Chef Automate will provide you with centralized, continuous configuration management.

Explanation

Elastic Load Balancing uses a Secure Socket Layer (SSL) negotiation configuration, known as a security policy, to negotiate SSL connections between a client and the load balancer. A security policy is a combination of SSL protocols, SSL ciphers, and the Server Order Preference option.

Explanation

Your VPC has an implicit router and a main route table that you can modify. Each subnet you create must be associated with a route table. Adding an internet gateway and adding a route to that IGW facilitates traffic out to the Internet for a public subnet. NAT instance and NAT gateways are provided to allow instances in private subnets to gain internet access

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

Amazon S3 encrypts your object before saving it on disks in its data centers and decrypts it when you download the objects. You have two options depending on how you choose to manage the encryption keys: Server-side encryption and client-side encryption. Server-side encryption is about data encryption at rest–that is, Amazon S3 encrypts your data as it writes it to disks inits data centers and decrypts it for you when you access it. As long as you authenticate your request and you have access permissions, there is no difference in the way you access encrypted or unencrypted objects. Amazon S3 manages encryption and decryption for you. For example, if you share your objects using a pre-signed URL, that URL works the same way for both encrypted and unencrypted objects. In client-side encryption, you manage encryption/decryption of your data, the encryption keys, and related tools. Server-side encryption is an alternative to client-side encryption in which Amazon S3 manages the encryption of your data, freeing you from thetasks of managing encryption and encryption keys. Amazon S3 server-side encryption employs strong multi-factor encryption. Amazon S3 encrypts each object with a unique key. As an additional safeguard, it encrypts the key itself with a masterkey that it regularly rotates. Amazon S3 server-side encryption uses one of the strongest block ciphers available, 256- bit Advanced Encryption Standard (AES-256), to encrypt your data

Explanation

yourwebsite.com is a zone apex. Alias record sets can be used to set a zone apex, but CNAME records cannot. Additionally, queries to Alias records that are mapped to an ELB are free. A records are used to map IPv4 addresses to FQDNs, the IP address of the ELB may change. MX records are used for email servers.

Explanation

AWS will choose the most specific route first. If routes are equal after checking for the most specific routes, AWS will use AS path prepending to determine which route is preferred. In this example, 10.20.30.0/25 is more specific than 10.20.30.0/24 and 10.20.0.0/16, so AS path prepending will not matter. The other options are either outside of the address range in question (10.20.30.128/26 and 10.20.128.0/17) or less specific than the route advertised by Houston (10.20.30.0/23). The route advertised from Orlando, 10.20.30.254/32, identifies a single IPv4 address that is outside of the range in question

Explanation

When using Amazon Import/Export, a separate job request needs to be submitted for each physical device even if they belong to the same import or export job.

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

You can create a VPC Gateway Endpoint to allow resources within a VPC to connect to DynamoDB without network communication extending outside your own VPC.

Explanation

You can secure your VPC instances using only security groups; however, you can add NACLs as a second layer of defense. Security groups — Act as a firewall for associated Amazon EC2 instances, controlling both inbound and outbound traffic at the instance level .  Network access control lists (NACLs) — Act as a firewall for associated subnets, controlling both inbound and outbound traffic at the subnet level . Security Groups supports allow rules only while Network Access Control Lists support allow and deny rules.

Explanation

EC2 Auto Recovery can detect any condition that will cause a system status check to fail, including hypervisor problems or loss of power/network connectivity.

Explanation

AWS is responsible for what is known as Security ‘of’ the Cloud. This covers their global infrastructure elements – Regions, Availability Zones, and Edge Locations, and also the foundations of their services covering Compute, Storage, Database, and Network

Explanation

Each subnet must be associated with a route table, which controls the routing for the subnet. If you don’t explicitly associate a subnet with a particular route table, the subnet is implicitly associated with the main route table. A route in the route table to an Internet Gateway marks the subnet as a public subnet and no route to an Internet Gateway marks the subnet as private.

Explanation

To host a static website, the user needs to configure an Amazon S3 bucket for website hosting and then upload the website contents to the bucket. The website is then available at the region-specific website endpoint of the bucket.

If the user has an index.html object as part of the bucket, the user can always host it without the website hosting feature. However, it will require an absolute URL of the object. In this case the user can access the whole bucket as a website and need not refer individual objects separately.

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

You can run Amazon RDS for Oracle under two different licensing models – “License Included” and “Bring-Your-Own-License (BYOL)”. In the “License Included” service model, you do not need separately purchased Oracle licenses; the Oracle Database software has been licensed by AWS.

Explanation

The ENI can only be attached to an instance hosted in a VPC. When you move a network interface from one instance to another, network traffic is redirected to the new instance. Some network and security appliances, such as load balancers, network address translation (NAT) servers, and proxy servers prefer to be configured with multiple network interfaces. You can create and attach secondary network interfaces to instances in a VPC that are running these types of applications and configure the additional interfaces with their own public and private IP addresses, security groups, and source/destination checking

Explanation

A route table contains a set of rules, called routes, that are used to determine where network traffic is directed.

Each subnet in your VPC must be associated with a route table; the table controls the routing for the subnet. A subnet can only be associated with one route table at a time, but you can associate multiple subnets with the same route table. When you add an Internet gateway, an egress-only Internet gateway, a virtual private gateway, a NAT device, a peering connection, or a VPC endpoint in your VPC, you must update the route table for any subnet that uses these gateways or connections.

Explanation

You can create an Auto Scaling group directly from an EC2 instance. When you use this feature, Auto Scaling automatically creates a launch configuration for you as well.

Explanation

When you send a request to initiate a multipart upload, Amazon S3 returns a response with an upload ID, which is a unique identifier for your multipart upload. You must include this upload ID whenever you upload parts, list the parts, complete an upload, or abort an upload. When uploading a part, in addition to the upload ID, you must specify a part number that uniquely identifies a part and its position in the object you are uploading. Amazon S3 returns an ETag header in its response. For each part upload, you must record the part number and the ETag value for use in each subsequent request.

Explanation

There are a few key points to this question:

1. Object locks can prevent objects from modification or deletion; objection versioning does not – it only maintains versions of an object until those versions are deleted.
2. Users can only enable Object locks can on new S3 buckets.
3. Object locks have two retention modes – governance mode and compliance mode. Compliance mode prevents objects from being deleted or updated by users, including the root user. Governance mode allows objects to be modified, but prevents objects from being deleted.

Explanation

Explanation

Several factors can affect the performance of Amazon EBS volumes, such as instance configuration, I/O characteristics, workload demand, and storage configuration. IOPS are input/output operations per second. Amazon EBS measures each I/O operation per second (that is 256 KB or smaller) as one IOPS. I/O operations that are larger than 256 KB are counted in 256 KB capacity units. For example, a 1,024 KB I/O operation would count as 4 IOPS. When you provision a 4,000 IOPS volume and attach it to an EBS-optimized instance that can provide the necessary bandwidth, you can transfer up to 4,000 chunks of data per second (provided that the I/O does not exceed the 128 MB/s per volume throughput limit of General Purpose (SSD) and Provisioned IOPS (SSD) volumes).

Explanation

In this case the alarm watches a metric every 5 minutes for 10 intervals. Thus, it needs at least 50 minutes to come to the “OK” state. Till then it will be in the INSUFFUCIENT_DATA state. Since 90 minutes have passed and CPU utilization is at 80% constant, the state of alarm will be “ALARM”.

Explanation

AWS provides customers with a PCI-compliant environment and the necessary tools to secure their environment. PCI compliance falls very much in line with the shared responsibility model. But ultimately, it is the customers responsibility to build and maintain a PCI-compliant environment.

Explanation

Persistent storage—If you need persistent virtual disk storage similar to a physical disk drive for files or other data that must persist longer than the lifetime of a single Amazon EC2 instance, Amazon EBS volumes or Amazon S3 are more appropriate. There is also the cost of data uploads as well as frequent transfers and downloads. While Glacier would be an effective archival service, the data may be accessed frequently, which would get expensive quickly for this start up.

Explanation

In AWS EC2, while configuring a security group, the user needs to specify the IP address in CIDR notation. The CIDR IP range 10.20.30.40/32 says it is for a single IP 10.20.30.40. If the user specifies the IP as 10.20.30.40 only, the security group will not accept and ask it in a CIDR format

Explanation

Amazon Glacier and S3 Standard-IA are both designed for storing infrequently accessed data. This is why the data storage fees are roughly one-half to one-sixth the cost of Standard Storage. Retrieval fees will quickly add up if the data is retrieved too often, so planning or correctly setting your object lifecycle based on how often you or your company will need the data is important.

Explanation

In Amazon Web Services, the spot instance is useful when the user wants to run a process temporarily. The spot instance can terminate the instance if the other user outbids the existing bid. In this case all storage is temporary and the data is not required to be persistent. Thus, the spot instance is a good option to save money

Explanation

Amazon S3 storage offers very high durability, but it is still a best practice to protect against user level deletion or overwriting of data using versioning, cross-region replication, and MFA Delete.

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

After you launch an instance in EC2-Classic, you can’t change its security groups. However, you can add rules to or remove rules from a security group, and those changes are automatically applied to all instances that are associated with the security group

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

Amazon CloudWatch provides the functionality to graph the metric data generated either by the AWS services or the custom metric to make it easier for the user to analyse. The AWS CloudWatch console provides the option to change the granularity of a graph and zoom in to see data over a shorter time period. To zoom, the user has to click in the graph details pane, drag on the graph area for selection, and then release the mouse button.

Explanation

Explanation

For protecting the Amazon EBS data at REST, the user can use options, such as Data Encryption (Windows / Linux / third party based), Data Replication (AWS internally replicates data for redundancy), and Data Snapshot (for point in time backup). Reference: http://media.amazonwebservices.com/AWS_Security_Best_Practices.pdf

Explanation

You restrict access to Amazon S3 content by creating an origin access identity, which is a special CloudFront user. You change Amazon S3 permissions to give the origin access identity permission to access your objects, and to remove permissions from everyone else. When your users access your Amazon S3 objects using CloudFront URLs, the CloudFront origin access identity gets the objects on your users’ behalf. If your users try to access objects using Amazon S3 URLs, they’re denied access. The origin access identity has permission to access objects in your Amazon S3 bucket, but users don’t.

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

DynamoDB tables are portioned based on the following: First, calculate total RCU/3000 + total WCU/1000. Then calculate the total size/10 GB. Then round up the higher of the two results

Explanation

Amazon EC2 allows you to set up and configure everything about your instances from your operating system up to your applications. An Amazon Machine Image (AMI) is simply a packaged-up environment that includes all the necessary bits to set up and boot your instance. M1 and M3 Standard instances have the same ratio of CPU and memory, some reasons below as to why you would use one over the other. M3 instances provide better, more consistent performance that M1 instances for most use-cases. M3 instances also offer SSD-based instance storage that delivers higher I/O performance. M3 instances are also less expensive than M1 instances. Due to these reasons, we recommend M3 for applications that require general purpose instances with a balance of compute, memory, and network resources. However, if you need more disk storage than what is provided in M3 instances, you may still find M1 instances useful for running your applications

Explanation

Elastic Load Balancing uses a Secure Socket Layer (SSL) negotiation configuration, known as a security policy, to negotiate SSL connections between a client and the load balancer. A security policy is a combination of SSL protocols, SSL ciphers, and the Server Order Preference option.

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

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

Turning off automatic backups or logging on the target database during the migration will help increase the speed of the initial migration load.

Explanation

Read replicas of your master database allow you to increase performance. Placing your read replicas in different AWS regions closer to your users will maximize performance and increase the availability of your database.

Explanation

The Simple Monthly Calculator is used to calculate projected costs, assuming you know what AWS resources you’ll be consuming.

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

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

To create a NAT gateway, you must specify the public subnet in which the NAT gateway will reside.  You must also specify an Elastic IP address to associate with the NAT gateway when you create it. After you’ve created a NAT gateway, you must update the route table associated with one or more of your private subnets to point Internet-bound traffic to the NAT gateway. This enables instances in your private subnets to communicate with the Internet.

Each NAT gateway is created in a specific Availability Zone and implemented with redundancy in that zone. You have a limit on the number of NAT gateways you can create in an Availability Zone.

Explanation

With IAM, you can centrally manage users, security credentials such as access keys, and permissions that control which AWS resources users can access. In some cases, you might have an IAM user with full access to IAM and Amazon S3. If the IAM user assigns a bucket policy to an Amazon S3 bucket and doesn’t specify the root user as a principal, the root user is denied access to that bucket. However, as the root user, you can still access the bucket by modifying the bucket policy to allow root user access.

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

When you create a bucket or object in Amazon S3, only you have access. To give control to others you can use course grained controls (Access Control Lists), and fine grained controls (bucket policies, IAM policies, and query-string authentication)

Explanation

In Hybrid cloud environment where connectivity between AWS and Corporate datacenter is critical, redundant active/active or active/passive configurations should be implemented for connectivity resources. redundancy has to be on both sides (AWS and On-premises) hence the minimum requirements to implement this architecture is two direct connect lines and two customer devices (ideally in two different data centers)

Explanation

To better control scale-out events, you can create a step scaling policy that dictates different levels of scaling based on different utilization levels of a metric you’ve selected.

Adjusting the cooldown period also minimizes the likelihood of scaling out again before the instances that were deployed in a previous scale out event have had time to warm up and handle requests to their full capability.

Explanation

Amazon CloudWatch Alarms have three possible states: OK: The metric is within the defined threshold ALARM: The metric is outside of the defined threshold INSUFFICIENT_DATA: The alarm has just started, the metric is not available, or not enough data is available for the metric to determine the alarm state

Explanation

Elastic Load Balancing supports both Internet Protocol version 6 (IPv6) and Internet Protocol version 4 (IPv4). Clients can connect to the user’s load balancer using either IPv4 or IPv6 (in EC2-Classic) DNS. However, communication between the load balancer and its back-end instances uses only IPv4. The user can use the Dualstack-prefixed DNS name to enable IPv6 supportfor communications between the client and the load balancers. Thus, the clients are able to access the load balancer using either IPv4 or IPv6 as their individual connectivity needs dictate.

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

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

Explanation

Amazon Route 53 lets you configure DNS failover in active-active, active-passive, and mixed configurations to improve the availability of your application. When you have more than one resource performing the same function, you can configure Amazon Route 53 to check the health of your resources and respond to DNS queries using only the healthy resources.

Another solution would be to assign an elastic IP address to the EC2 instance and have a backup instance running. In the event of failure, move the Elastic IP from the primary instance to the backup instance.

Explanation

An Elastic IP address is associated with your AWS account. With an Elastic IP address, you can mask the failure of an instance or software by rapidly remapping the address to another instance in your account. You can disassociate an Elastic IP address from a resource, and reassociate it with a different resource. A disassociated Elastic IP address remains allocated to your account until you explicitly release it. An Elastic IP address is for use in a specific region only.

Explanation

You are billed per-second with a one-minute minimum for On-Demand, Spot and Reserved instances as long as your EC2 instance is in a running state, provided the instance is Linux (with some exceptions), and not a Windows operating system, in which case the instance would be billed per-hour.

Explanation