AWS Developer Associate Exam Notes Part 2

For more information on AWS, visit aws.amazon.com

Storage:

S3 (Simple Storage Service):

Amazon Simple Storage Service (Amazon S3), provides developers and IT teams with secure, durable, highly-scalable cloud storage. Amazon S3 is easy to use object storage, with a simple web service interface to store and retrieve any amount of data from anywhere on the web.

This topic is covered in AWS Solutions Architect Study Guide
Object based storage only for files, can not install OS or applications
Data is spread across multiple devices and multiple facilities
Can loose 2 facilities and still have access to your files
Files can be between 1 byte and 5TB, and has no storage limit
Files are stored flatly in buckets, Folders don't really exist, but are part of the file name
S3 bucket names have a universal name-space, meaning each bucket name must be globally unique
S3 Stores data in alphabetical order (lexigraphical order)
S3 URL structures are region/amazon.aws.com/bucketname (https://s3-eu-west-1.amazonaws.com/myawesomebucket)
Read after write consistency for PUTS of new objects (As soon as you write an object, it is immediately available)
Eventual consistency for overwrite PUTS and DELETES. (Updating or deleting an object could take time to propagate)
S3 is basically a key value store and consists of the following:
- Key - Name of the object
- Value - Data made up of bytes
- Version ID (important for versioning)
- Meta-data - Data about what you are storing
- ACLs - Permissions for stored objects
Amazon guarantees 99.99% availability for the S3 platform
Amazon guarantees 99.999999999% durability for S3 information (11 x 9's)
Tiered storage, and life-cycle management available
Versioning is available but must be enabled. It is off by default
Offers encryption, and allows you to secure the data using ACLs
S3 charges for storage, requests, and data transfer
Bucket names must be all lowercase, however in US-Standard if creating with the CLI tool, it will allow capital letters
The transfers tab shows uploads, downloads, permission changes, storage class changes, etc..
When you upload a file to S3, by default it is set private
You can transfer files up to 5GB using PUT requests
You can setup access control to control your buckets access by using bucket policies or ACLs
Change the storage class under the Properties tab when an object is selected
S3 buckets can be configured to create access logs which logs all requests to the S3 bucket
S3 Events include SNS, or SQS events or Lambda functions. Lambda is location specific, not available in South Korea
All storage tiers have SSL support, millisecond first byte latency, and support life-cycle management policies.
Storage Tiers:
- Standard S3:
  - Stored redundantly across multiple devices in multiple facilities
  - Designed to sustain the loss of 2 facilities concurrently
  - 11-9's durability, 99.99% availability
- S3-IA (Infrequently Accessed):
  - For data that is accessed less frequently, but requires rapid access when needed
  - Lower fee than S3, but you are charged a retrieval fee
  - Also designed to sustain the loss of 2 facilities concurrently
  - 11-9's durability, 99.99% availability
- Reduced Redundancy Storage (RSS):
  - Use for data such as thumbnails or data that could be regenerated
  - Costs less than Standard S3
  - Designed to provide 99.99% durability and 99.99% availability of objects over a year
  - Designed to sustain the loss of a single facility
- Glacier:
  - Very cheap, Stores data for as little as $0.01 per gigabyte, per month
  - Optimized for data that is infrequently accessed. Used for archival only
  - It takes 3-5 hours to restore access to files from Glacier
Versioning and Cross-Region Replication (CRR):
- Versioning must be enabled in order to take advantage of Cross-Region Replication
- Versioning resides under Cross Region Replication tab
- Once Versioning is turned on, it can not be turned off, it can only be suspended
- If you truly wanted versioning off, you would have to create a new bucket and move your objects
- When versioning is enabled, you will see a slider tab at the top of the console that will enable you to hide/show all versions of files in the bucket
- If a file is deleted for example, you need to slide this tab to show in order to see previous versions of the file
- With versioning enabled, if you delete a file, S3 creates a delete marker for that file, which tells the console to not display the file any longer
- In order to restore a deleted file you simply delete the delete marker file, and the file will then be displayed again in the bucket
- To move back to a previous version of a file including a deleted file, simply delete the newest version of the file or the delete marker, and the previous version will be displayed
- Versioning does store multiple copies of the same file. So in the example of taking a 1MB file, and uploading it. Currently your storage usage would be 1MB. Now if you update the file with small tweeks, so that content changes, but the size remains the same, and upload it. With the version tab on hide, you will see only the single updated file, however if you select show on the slider, you will see that both the original 1MB file exists as well as the updated 1MB file, so your total S3 usage is now 2MB not 1MB
- Versioning does NOT support de-duplication or any similar technology currently
- For Cross Region Replication (CRR), as long as versioning is enabled, clicking on the tab will now give you the ability to suspend versioning, and enable cross region replication
- Cross Region Replication (CRR) has to be enabled on both the source and destination buckets in the selected regions
- Destination bucket must be created and again globally unique (can be created right from the versioning tab, in the CRR configuration section via button)
- You have the ability to select a separate storage class for any Cross Region Replication destination bucket
- CRR does NOT replicate existing objects, only future objects meaning that only objects stored post turning the feature on will be replicated
- Any object that already exists at the time of turning CRR on, will NOT be automatically replicated
- Versioning integrates with life-cycle management and also supports MFA delete capability. This will use MFA to provide additional security against object deletion
Life-cycle Management:
- When clicking on Life-cycle, and adding a rule, a rule can be applied to either the entire bucket or a single 'folder' in a bucket
- Rules can be set to move objects to either separate storage tiers or delete them all together
- Can be applied to current version and previous versions
- If multiple actions are selected for example transition from STD to IA storage 30 days after upload, and then Archive 60 days after upload is also selected, once an object is uploaded, 30 days later the object will be moved to IA storage. 30 days after that the object will be moved to glacier.
- Calculates based on UPLOAD date not Action data
- Transition from STD to IA storage class requires MINIMUM of 30 days. You can not select or set any data range less than 30 days
- Archive to Glacier can be set at a minimum of 1 day If STD->IA is NOT set
- If STD->IA IS set, then you will have to wait a minimum of 60 days to archive the object because the minimum for STD->IA is 30 days, and the transition to glacier then takes an additional 30 days
- When you enable versioning, there will be 2 sections in life-cycle management tab. 1 for the current version of an object, and another for previous versions
- Minimum file size for IA storage is 128K for an object
- Can set policy to permanently delete an object after a given time frame
- If versioning is enabled, then the object must be set to expire, before it can be permanently deleted
- Can not move objects to Reduced Redundancy using life-cycle policies
S3 Transfer Acceleration:
- Utilizes the CloudFront Edge Network to accelerate your uploads to S3
- Instead of uploading directly to your S3 bucket, you can use a distinct URL to upload directly to an edge location which will then transfer the file to S3
- Transfer Acceleration URLs will have the format of bucketname.s3-accelerate.amazonaws.com
- There is a test utility available that will test uploading direct to S3 vs through Transfer Acceleration, which will show the upload speed from different global locations
- Turning on and using Transfer Acceleration will incur an additional fee
2 types of encryption available:
- In transit:
  - Uses SSL/TLS to encrypt the transfer of the object
- At Rest (AES 256):
  - Server Side: S3 Manged Keys (SSE-S3)
  - Server Side: AWS Key Management Service, Managed Keys (SSE-KMS)
  - Server Side: Encryption with Customer provided Keys (SSE-C)
  - Client Side Encryption
Pricing (What your charged for when using S3):
- Storage used
- Number of Requests
- Data Transfer

Developer Associate Specific Topics

Web Hosting:
- Used for static hosting only; Server side code will not execute
- Don't need to worry about scaling, ELBs or number of instances, S3 handles all of that for you
- When you create an S3 bucket or enable hosting, you still need to make sure that either the files or the entire bucket are set to public accesibility
- Bucket URLs are structured such as https://s3-eu-west-1.amazonaws.com/somebucketname
- Hosted site URLs are structured as http://somebucketname.s3-website-eu-west-1.amazonaws.com
- Hosting sites on S3 does not allow HTTPS support
- Sites hosted on S3 can be served via HTTPS if distributed by cloudfront; Cloudfront would be configured to terminate a client HTTPS requst, and then talk to the bucket via standard HTTP
- Can be configured to redirect to another URL
CORS Configuration:
- Cross Origin Resource Sharing (CORS)
- Configured in the permisssions section of the properties tab in a bucket
- CORS configuration is in XML format and will be pasted directly into the permissions
- CORS is required if you are calling an asset that resides in another bucket from the bucket that your static site resides in using the hosted URL

Resource or Operation	Default Limit
Buckets per account:	100
Largest files size you can transfer with PUT request:	5GB
Minimum file size:	1 byte
Maximum file size:	5 TB

For additional information about API Gateway Limits, see Limits in Amazon S3

CloudFront:

Amazon CloudFront is a global content delivery network (CDN) service that accelerates delivery of your websites, APIs, video content or other web assets.

This topic is covered in AWS Solutions Architect Study Guide
Edge Location is the location where content will be cached, separate from an AWS Region/AZ
Origin is the origin of all files, can be S3, EC2 instance, a ELB, or Route53
Distribution is the name given to the CDN which consists a collection of edge locations
Web Distributions are used for websites
RTMP - (Real-Time Messaging Protocol) used for streaming media typically around adobe flash files
Edge locations can be R/W and will accept a PUT request on an edge location, which then will replicate the file back to the origin
Objects are cached for the life of the TTL (24 hours by default)
You can clear objects from edge locations, but you will be charged
When enabling cloudfront from an S3 origin, you have the option to restrict bucket access; this will disable the direct link to the file in the S3 bucket, and ensure that the content is only served from cloudfront
The path pattern uses regular expressions
You can restrict access to your distributions using signed URLS
You can assign Web Application Firewall rules to your distributions
Distribution URLs are going to be non-pretty names such as random_characters.cloudfront.com; you can create a CNAME that points to the cloudfront name to make the URL user friendly
You can restrict content based on geographical locations in the behaviors tab
You can create custom error pages via the error pages tab
Purging content is handled in the Invalidations tab

Resource or Operation	Default Limit
Data transfer rate per distribution:	40 Gbps
Requests per second per distribution:	100,000
Web distributions per account:	200
RTMP distributions per account:	100
Alternate domain names (CNAMEs) per distribution:	100
Origins per distribution:	25
Cache behaviors per distribution:	25
White-listed headers per cache behavior:	10
White-listed cookies per cache behavior:	10
SSL certificates per account when serving HTTPS requests using dedicated IP addresses (no limit when serving HTTPS requests using SNI):	2
Custom headers that you can have Amazon CloudFront forward to the origin:	10 name–value pairs

For additional information about CloudFront Limits, see Limits in Amazon CloudFront

Databases:

DynamoDB (No-SQL):

Fast and flexible NoSQL DB service for all apps that need consistent, single-digit millisecond latency at any scale. It is a fully managed database and supports both document and key-value data models. Its flexible data model and reliable performance make it a great fit for mobile, web, gaming, ad-tech, IoT, and many other applications.

This topic is covered in AWS Solutions Architect Study Guide
Non Relational DB (No-SQL), comprised of collections (tables), of documents (rows), with each document consisting of key/value pairs (fields)
Document oriented DB
Offers push button scaling, meaning that you can scale your db on the fly without any downtime
RDS is not so easy, you usually have to use a bigger instance size or add read replicas
Stored on SSD Storage
Spread across 3 geographically distinct data centers
Eventual Consistent Reads (Default)
- Consistency across all copies of data is usually reached within 1 second
- Repeating a read after a short time should return updated data
- Best Read Performance
Strongly Consistent Reads
- Returns a result that reflects all writes that received a successful response prior to the read
Structure:
- Tables
- Items (Think rows in a traditional table)
- Attributes (Think columns of data in a table)
Provisioned throughput capacity
Write throughput 0.0065 per hour for every 10 units
Read throughput 0.0065 per hour for every 50 units
First 25 GB of storage is free
Storage costs of 25 cents per additional GB per Month
Can be expensive for writes, but really really cheap for reads
The combined key/value size must not exceed 400 KB for any given document

Developer Associate Specific Topics

Supports attribute nesting up to 35 levels
Conditional writes are idempotent, you can send the same conditional write request multiple times, but it will have no further effect on the item after the first time Dynamo performs the update
Supports atomic counters, using the UpdateItem operation to increment or decrement the value of an existing attribute without interfering with other write requests
Atomic counter updates are not idempotent, the counter will increment each time you call UpdateItem
If you can have a small margin of error in your data, then use atomic counters
If your application needs to read multiple items, you can use the BatchGetItem API endpoint; A single request can retrieve up to 1MB of data with as many as 100 items
A single BatchGetItem request can retrieve items from multiple tables
All write requests are applied in the order in which they are received
Pricing (calculate the amount of writes and reads per second):
- Divide total number of writes per day / 25 (hours) / 60 (minutes) / 60 (seconds) = No. writes per second
- A write or read capacity unit can handle 1 write/read per second
- Individual items or the entire table can be exported to CSV
- Example:
  - Using 28 GB of storage
  - 1,000,000 writes per day = 1,000,000/24 = 41,666.67
  - 41,666.67 / 60 (minutes) = 694.44
  - 694.44 / 60 (seconds) = 11.574 writes per second
  - This example would require 12 write capacity units (single capacity unit is 1 write per second)
  - Charge for write is $0.0065 per 10 units
  - $0.0065 / 10 = $0.00065 per unit
  - $0.00065 * 12 (required write units) = $0.0078
  - $0.0078 * 24 (hours per day) = $0.1872 per day for writes
  - Charge for read is $0.0065 per 50 units
  - $0.0065 / 50 = $0.00013 per unit
  - $0.00013 * 12 (required read units) = $0.00156
  - $0.00156 * 24 (hours per day) = $0.03744 per day for reads
  - Using 28 GB storage with first 25 GB free = 3 GB storage required
  - 3 GB * $0.25 per GB (after initial 25) = $0.75
Indexes:
- Primary Key types:
  - Single attribute (unique ID):
    - Partition Key (Hash Key composed of one attribute)
    - Partition Key's value is used as input to an internal hash function which output determines the partition (physical location in which the data is stored)
    - No 2 items in a table can have the same partition key value
  - Composite (unique ID and date range):
    - Partition Key & Sort Key (Hash and Range) composed of two attributes
    - Partition Key's value is used as input to an internal hash function which output determines the partition (physical location in which the data is stored)
    - 2 Items can have the same partition key, but they MUST have a different sort key
    - All Items with the same partition key are stored together, in sorted order by the sort key value
- Local Secondary Index (LSI):
  - Has the SAME partition key, but different sort key
  - Can ONLY be created when creating a table
  - Can not be removed or modified after creation
  - Can have up to 5 LSI's per table
- Global Secondary Index (GSI):
  - Has DIFFERENT partition key and different sort key
  - Can be created at table creation or added LATER
  - Can have up to 5 GSI's per table
Streams:
- Used to capture any kind of modification of the DynamoDB tables
- If new item is added to the table, the stream captures an image of the entire item, including all of its attributes
- If an item is updated, the stream captures the before and after image of any attributes that were modified in the item
- If an item is deleted from the table, the stream captures an image of the entire item before it was deleted
- Streams are stored for 24 hours and then is lost
- Streams can trigger functions with Lambda that will perform actions based on the instantiation of a stream event
Query's:
- Operation that finds items in a table using only the primary key attribute value
- Must provide a partition attribute name and distinct value to search for
- Optionally can provide a sort key attribute name and value and use comparison operator to refine the search results
- By default a query returns all of the data attributes for items with the specified primary key(s)
- The ProjectionExpression parameter can be used to only return some of the attributes from a query as opposed to the default all
- Results are always sorted by the sort key
- If the data type of the sort key is a number, the results are returned in numeric order
- If the data type of the sort key is a string, the results are returned in order of ASCII character code values
- Sort order is ascending, the ScanIndexForward parameter can be set to false to sort in descending order
- By default queries are eventually consistent but can be changed to strongly consistent
- More efficient then a scan operation
- For quicker response times, design your tables in a way that can use the query, GET, or BatchGetItem API
Scans:
- Examines every item in the table
- By default, a scan returns all of the data attributes for every item
- Can use the ProjectionExpression parameter so that the scan only returns some of the attributes, instead of all
- Always scans the entire table, then filters out values to provide the desired result (added step of removing data from initial dataset)
- Should be avoided on a large table with a filter that removes many results
- As table grows, the scan operation slows
- Examines every item for the requested values, and can use up provisioned throughput for a large table in a single operation
Provisioned Throughput
- 400 HTTP status code - ProvisionedThroughputExceededException error will indicate that you exceeded your max allowed provisioned throughput for a table or for one or more GSI's
- Unit of read provisioned throughput:
  - All reads are rounded up to increments of 4 KB
  - Eventual consistent reads (default) consist of 2 reads per second
  - Strongly consistent reads consist of 1 read per second
  - Take the (size of the read rounded to the nearest 4 KB chunk / 4 KB) * No. of items = read throughput
  - Divide by 2 if eventually consistent
  - Example:
    - Application requires to read 10 items of 1 KB per second using eventual consistency, whats the read throughput
    - Calculate the number of read units per item needed
    - 1 KB rounded to the nearest 4 KB increment = 4 (KB) or a single chunk
    - 4 KB / 4 KB = 1 read unit per item
    - 1 x 10 read items = 10
    - Using eventual consistency is 10 /2 = 5
    - 5 units of read throughput
  - Example 2:
    - Application requires to read 10 items of 6 KB per second using eventual consistency, whats the read throughput
    - Calculate the number of read units per item needed
    - 6 KB rounded to the nearest 4 KB increment = 8 (KB) or 2 chunks of 4 KB
    - 8 KB / 4 KB = 2 read unit per item
    - 2 x 10 read items = 20
    - Using eventual consistency is 20 /2 = 10
    - 10 units of read throughput
- Unit of write provisioned throughput:
  - All writes are 1 KB
  - All writes consist of 1 write per second
  - Example:
    - Application requires to write 5 items with each being 10KB in size per second
    - Each write unit consists of 1 KB of data, need to write 5 items per second with each item using 10 KB of data
    - 5 items * 10 KB = 50 write units
    - Write throughput is 50 units
  - Example 2:
    - Application requires to write 12 items with each being 100KB in size per second
    - Each write unit consists of 1 KB of data, need to write 12 items per second with each item using 100 KB of data
    - 12 items * 100 KB = 1200 write units
    - Write throughput is 1200 units
Web Identity Providers:
- Authenticate users using Web Identity Providers such as Facebook, Google, Amazon or any other ID Connect-compatible identity provider
- Accomplished using AssumeRoleWithWebIdentity API
- Need to create a role first
- Process:
  - User authentication request sent and received with the identity provider such as Facebook, Google, etc..
  - Web Identity token returned from provider
  - Token, App ID of provider, and ARN of IAM Role sent to AssumeRoleWithIdentity API endpoint
  - AWS issues temporary security credentials back to the user allowing the user to access resources (1 hour default)
  - Temporary security credentials response consist of 4 things:
    - AccessKeyID, SecretAccessKey, SessionToken
    - Expiration (time limit, 1 hour by default)
    - AssumeRoleID
    - SubjectFromWebIdentityToken

US East (N. Virginia) Region	Default Limit
Maximum capacity units per table or global secondary index:	40,000 read capacity units and 40,000 write capacity units
Maximum capacity units per account:	80,000 read capacity units and 80,000 write capacity units

All Region Resource or Operation	Default Limit
Maximum capacity units per table or global secondary index:	10,000 read capacity units and 10,000 write capacity units
Maximum capacity units per account:	20,000 read capacity units and 20,000 write capacity units
Maximum number of tables:	256

For additional information about DynamoDB Limits, see Limits in Amazon DynamoDB

Security and Identity:

IAM (Identity and Access Management):

AWS Identity and Access Management (IAM) enables you to securely control access to AWS services and resources for your users.

This topic is covered in AWS Solutions Architect Study Guide
Allows for centralized control and shared access to your AWS Account and/or AWS services
By default when you create a user, they have NO permissions to do anything
Root account has full admin access upon account creation
Not region specific, can be shared between all regions
Granular permission sets for AWS resources
Includes Federation Integration which taps into Active Directory, Facebook, Linkedin, etc. for authentication
Multi-factor authentication support
Allows configuration of temporary access for users, devices and services
Set up and manage password policy and password rotation policy for IAM users
Integration with many different AWS services
Supports PCI DSS compliance
Access can be applied to:
- Users - End users (people)
- Groups - Collection of users under one set of permissions
- Roles - Assigned to AWS resources, specifying what the resource (such as EC2) is allowed to access on another resource (S3)
- Policies - Document that defines one or more permissions
Policies can be applied to users, groups and roles
You can assign up to 10 policies to a single group
Policy documents must have a version, and a statement in the body; The statement must consist of Effects (Allow, Deny), Actions(Which action to allow/deny such a * for all actions), and Resources (affected resources such as * for all resources)
All resources can share the same policy document
There are 3 different types of roles:
- Service Roles
- Cross account access roles
  - Used when you have multiple AWS accounts and another AWS account must interact with the current AWS account
- Identity provider access roles
  - Roles for facebook or similar Identity providers
In order for a new IAM user to be able to log into the console, the user must have a password set
By default a new users access is only accomplished through the use of the access key/secret access key
If the users password is a generated password, it also will only be shown at the time of creation.
Customizable Console Sign-in link can be configured on the main IAM page (aws.yourdomain.com)
Customizable Console Sign-in links must be globally unique. If a sign in link name is already taken, you must choose an alternative
Root account is email address that you used to register your account
Recommended that root account is not used for login, and should be secured with Multi-factor Authentication (MFA)
Can create Access Keys/ Secret Access Keys to allow IAM users (or service accounts) to be used with AWS CLI or API calls
Access Key ID is equivalent to a user-name, Secret Access Key is equivalent to a password
When creating a user's credentials, you can only see/download the credentials at the time of creation not after.
Access Keys can be retired, and new ones can be created in the event that secret access keys are lost
To create a user password, once the users have been created, choose the user you want to set the password for and from the User Actions drop list, click manage password. Here you can opt to create a generated or custom password. If generated, there is an option to force the user to set a custom password on next login. Once a generated password has been issued, you can see the password which is the same as the access keys. Its shown once only
Click on Policies from the left side menu and choose the policies that you want to apply to your users. When you pick a policy that you want applied to a user, select the policy, and then from the top Policy Actions drop menu, choose attach and select the user that you want to assign the policy to

Resource or Operation	Default Limit
Groups per account:	100
Instance profiles:	100
Roles:	250
Server Certificates:	20
Users:	5000
Number of policies allowed to attach to a single group:	10

For additional information about API Gateway Limits, see Limits in IAM entities and objects

Directory Service:

AWS Directory Service makes it easy to setup and run Microsoft Active Directory (AD) in the AWS cloud, or connect your AWS resources with an existing on-premises Microsoft Active Directory.

Active Directory flow is initialted when a user browses to the ADFS integrated site:
- The sign-on page will authenticate the user against Active Directory
- Depending on the browser used, the user may be promted to input their AD username/password
- The users browser receives a SAML (Secure Assertive Markup Language) assertion in the form of an auth response from AD Federation Services (ADFS)
- The users browser posts the SAML assertion to the AWS sign-in endpoint for SAML
- The AWS console uses the AssumeRoleWithSAML API to request temporary security credentials and then constructs a sign-in URL for the AWS Console
- The users browser receives the sign-in URL and is redirected to the conole
- The process is transparent to the user; They start at an interanl web site and end up on the console without having to supply credentials
- Remember the API call to request temporary security credentials from the AWS platform is AssumeRoleWithSAML
- The sign-in endpoint for SAML is https://signin.aws.amazon.com/saml
When using ADFS the user always authenticates with AD first before recieving security credentials
Web Identity Federation:
- Allows users to authenticate your application with Facebook, LinkedIn, Google, or your AWS account
- The AWS console has a link to a Web Identity Federation Playground, that allows you to test logins using services such as FB, LinkedIn, etc...
- Once logged in using the playground, you get a response containing an accessToken that is good for 5016 seconds
- This went to the service such as FB, authenticated with the service, recieved an accessToken, using the token, AWS will grant temporary security credentials by making an AssumeRoleWithWebIdentity request
- When the AssumeRoleWithWebIdentity request is formed, a trust policy is created granting all access via the recieved accessToken
- Authenticate with web service (facebook, etc..) first, then get temporary security credentials via AccessToken sent to AssumeRoleWithWebIdentity request, and finally with the temporary security credentials, user is able to access AWS resources
- Remember the API call to request temporary security credentials from the AWS platform is AssumeRoleWithWebIdentity

Management Tools:

Cloud Formation:

AWS CloudFormation gives developers and systems administrators an easy way to create and manage a collection of related AWS resources, provisioning and updating them in an orderly and predictable fashion.

This topic is covered in AWS Solutions Architect Study Guide
Deploy application as stacks. Much like a docker-compose file for docker
Can be written in either JSON or YAML
Free service, however resources created by CloudFormation are subject to normal pricing
Fn::GetAtt is a function that will allow you to get attributes of newly launched resources from CloudFormation such as DNS name, IP address, etc..
If errors are encountered the stack launch will terminate and rollback all resources that were created

Resource or Operation	Default Limit
Stacks:	200

For additional information about Cloud Formation Service Limits, see Limits in Amazon CloudFormation

Application Services:

SQS (Simple Queue Service):

Web service that gives you access to a message queue that can be used to store messages while waiting for a computer to process them. SQS is a distributed queue system that enables applications to quickly and reliably queue messages that one component of the application generates to be consumed by another component. A queue is a temp repository for messages that are awaiting processing.

This topic is covered in AWS Solutions Architect Study Guide
Used to allow customers the ability to decouple infrastructure components
Very first service AWS released. Even older then EC2
Messages can contain up to 256 KB of text in any format
Acts as a buffer between the component producing and saving data, and the component receiving and processing the data
Ensures deliver of each message at least once and supports multiple readers and writers interacting with the same queue
A single queue can be used simultaneously by many distributed application components, with no need for those components to coordinate or communicate with each other
Will always be available and deliver messages
Does not guarantee FIFO delivery of messages
Messages can be delivered multiple times and in any order
FIFO is not supported
If sequential processing is a requirement, sequencing information can be placed in each message so that message order can be preserved
SQS always asynchronously PULLs messages from the queue
Retention period of 14 days
12 hour visibility timeout by default
If you find that the default visibility timeout period (12 hours) is insufficient to fully process and delete the message, the visibility timeout can be extended using the ChangeMessageVisibility action
If the ChangeMessageVisibility action is specified to set an extended timeout period, SQS restarts the timeout period using the new value
Engineered to provide delivery of all messages at least one
Default short polling will return messages immediately if messages exist in the queue
Long polling is a way to retrieve messages from a queue as soon as they are available; long polling requests don't return a response until a message arrives in the queue
Maximum long poll time out is 20 seconds
256kb message sizes (originally 64kb)
Billed for 64kb chunks
First million messages free, then $.50 per additional million thereafter
Single request can have from 1 to 10 messages, up to a max payload of 256KB
Each 64KB chunk of payload is billed as 1 request. If you send a single API request with a 256KB payload, you will be billed for 4 requests (256/64 KB chunks)
"Decouple" = SQS on exam
Auto-scaling supported
Message prioritization is not supported
Process:
- Component 1 sends a message to the queue
- Component 2 retrieves the message from the queue and starts the visibility timeout period
- Visibility timer only starts when the message is picked up from the queue
- Component 2 processes the message and then deletes it from the queue during the visibility timeout period
- If the visibility timeout period expires, the message will stay in the queue and not be deleted
- The process is only complete when the queue receives the command to delete the message from the queue

For additional information about SQS Limits, see Limits in Amazon SQS

SWF (Simple Workflow Service)

Simple Workflow Service is a web service that makes it easy to coordinate work across distributed application components. Enabled for a range of uses such as media processing, web back ends, business process work-flows, and analytics pipelines, all to be designed as a coordination of tasks. Tasks represent invocations of various processing steps in an application which can be performed by code, API calls, human action and scripts.

This topic is covered in AWS Solutions Architect Study Guide
Build, run and scale background jobs or tasks that have sequential steps
Way to process human oriented tasks using a framework
SQS has a retention period of 14 days, vs SWF has up to a 1 year for work-flow executions
Workflow retention is always shown in seconds (3.1536E+07 seconds)
"Task could take a month" = SWF, as SQS only has a 14 day retention
Presents a task-oriented API, whereas SQS offers a message-oriented API
Ensures a teaks is assigned only once and is never duplicated; SQS duplicate messages are allowed, and must be handled
Keeps track of all tasks and events in an application, SQS would need an implementation of a custom application-level tracking mechanism
A collection of work-flows is referred to as a domain
Domains isolate a set of types, executions, and task lists from others within the same account
You can register a domain by using the AWS console or using the RegisterDomain action in the SWF API
Domain parameters are specified in JSON format
SWF Actors:
- Workflow starters - An application that can initiate a Workflow
- Decider's - Control the flow or coordination of activity tasks such as concurrency, or scheduling in a work-flow execution; If something has finished in a work-flow (or fails), a decider decides what to do next
- Activity Workers - Programs that interact with SWF to get tasks, process received tasks, and return the results
Brokers the interactions between workers and the decider; Allows the decider to get consistent views into the progress of tasks and to initiate new tasks in an ongoing manner
Stores tasks, assigns them to workers when they are ready and monitors their progress
Ensures that a task is assigned only once and is never duplicated
Maintains the application state durably, workers and decider's don't have to keep track of the execution state, and can run independently, with the ability to scale quickly

For additional information about SWF Limits, see Limits in Amazon SWF

Mobile Services:

SNS (Simple Notification Service):

Simple Notification Service is a web service that makes it easy to set up, operate, and send notifications from the cloud. It provides developers with a highly scalable, flexible, and cost-effective capability to publish messages from an application and immediately deliver them to subscribers or other applications.

Web service that allows customers to setup, operate, and send notifications from the cloud
Can push to Apple, Google, FireOS, and Windows devices, as well as Android devices in China with Baidu cloud push
Follows the publish-subscribe (pub-sub) messaging paradigm, with notifications being delivered to clients using a push mechanism that eliminates the need to poll for updates
Can deliver notifications by SMS, email, SQS queues, or any HTTP endpoint
SNS notifications can be used to trigger lambda functions
When a message is published to an SNS topic that has a lambda function subscribed to it, the function is invoked with the payload of the published message. The lambda function would receive the message payload as an input parameter, and can manipulate the info in the message, publish the message to other SNS topics or send the message to other AWS services
Allows you to group multiple recipients using topics
Topics are access points for allowing recipients to dynamically subscribe for copies of the notification
One topic can support deliveries to multiple endpoint types, for example, IOS, Android, and SMS recipients can be grouped together
When message is published, SNS delivers appropriately formatted copies of your message to each subscriber
Email notifications will be JSON formated not XML
Subscriptions have to be confirmed
Subscription expire after 3 days if they are not confirmed
TTL is the number of seconds since the message was published
If the message is not delivered within the TTL time, then the message will expire
To prevent messages from being lost, all messages published to SNS are stored redundantly across multiple AZ's
Instantaneous, PUSH based delivery (No Polling) --> SQS requires polling
Simple API and easy integration with applications
Flexible message deliver over multiple transport protocols
Inexpensive, pay as you go model
Web based AWS management console offers simplicity of point and click interface
$.50 per million SNS requests
$.06 per 100,000 notification deliveries over HTTP
$0.75 per 100 notifications over SMS
$2.00 per 100,000 notification deliveries over email
Can be used in conjunction with SQS to fan a single message out to multiple SQS queues
Remember:
- SNS - PUSH
- SQS - PULL (poll)
Subscribers:
- HTTP
- HTTPS
- Email
- Email-JSON
- SQS
- Application
- Lambda
- Messages can be customized for each of the available protocols

Resource or Operation	Default Limit
Topics :	100,000
Account spend threshold for SMS:	50 USD
Delivery rate for promotional SMS messages:	20 Messages per second
Delivery rate for transactional SMS messages:	20 Messages per second

White Paper Review:

Shared security model
- AWS:
  - Responsible for securing the underlying infrastructure
  - Responsible for protecting the global infrastructure that runs all of the services offered on the AWS cloud.
  - Infrastructure comprised of hardware, software, networking, and facilities that run AWS services
  - Responsible for the security configuration of its products that are considered managed services, such as DynamoDB, RDS, Redshift, Elastic MapReduce, lambda, and Workspaces.
- User:
  - Responsible for anything put on the cloud
  - EC2, VPC, S3 security configuration and management tasks
  - Account Management (MFA, SSL, TLS, CloudTrail API/User activity logging)