Applications Flashcards

1
Q

What is SQS?

A

A pull based 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. Each message is limited to 256 kb in size.

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2
Q

True or False. Using Amazon SQS, you can decouple the components of an application so they run independently, easing message management between components.

A

True. The word decouple usually leads to SQS.

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3
Q

What is a standard queue?

A

Nearly-unlimited number of transactions per second. Occasionally more than one copy of a message might be delivered out of order.

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4
Q

What is a FIFO queue?

A

First in first out delivery and exactly-once processing. Duplicates are not introduced into the queue. Limited to 300 transaction per second

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5
Q

When should you use FIFO queue over standard queue?

A
  1. If the order of processing matters
  2. If you would not want something to be processed more than once (even accidentally)
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6
Q

What is visibility timeout with SQS?

A

The amount of time that the message is invisible in the SQS queue after a reader picks up that message. Provided the job is processed before the visibility timeout expires, the message will then be deleted from the queue. If the job is not processed within that time, the message will become visible again and another reader will process it. This could result in the same message being delivered twice.

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7
Q

What is SQS long polling?

A

A way to retrieve messages from your Amazon SQS queues. While the regular short polling returns immediately (even if the message queue being polled is empty), long-polling doesn’t return a response until a message arrives in the message queue, or the long poll times out. This is a way to save money. Will help your EC2 not have to constantly poll the SQS queue.

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8
Q

What is SWF?

A

Simple Work Flow Service. A web service that makes it easy to coordinate work across distributed application components. SWF enables applications for a range of use cases, including media processing, web application back-ends, business process workflows, and analytics pipelines, to be designed as coordination of tasks.

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9
Q

What is the difference between SQS and SWF? List 4

A
  • SQS has a retention period of up to 14 days; with SWF, workflow executions can last up to a year
  • SWF presents a task-oriented API, whereas SQS offers a message-oriented API
  • SWF ensures that the task is assigned only once and never duplicated. SQS needs to handle duplicated messages and may also need to ensure that a message is processed only once
  • SWF keeps track of all the tasks and events in an application. SQS you need to implement your own application-level tracking especially if your application uses multiple queues
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10
Q

What are the different SWF actors?

A
  • Workflow starters - initiate the workflow
  • Deciders - control the flow of activity tasks
  • activity workers - carry out activity tasks
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11
Q

What is SNS?

A

Simple Notification Service. Service that makes it easy to set up, operate, and send notifications from the cloud. Can work wtih several endpoints:

  • SMS text message
  • Email to SQS queues
  • HTTP endpoints
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12
Q

True or False. SNS allows you to group multiple recipients using topics.

A

True. The topic is an access point for allowing recipients to dynamically subscribe for identical copies of the same notification.

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13
Q

What is Elastic Transcoder?

A

Media transcoder in the cloud. Convert media files from their original source format into different formats that will play on smartphones, tablets, PCs, etc. Provides transcoding presets for popular output formats, which means that you don’t need to guess about which settings work best on particular devices. Pay based on the minutes and resolution that you transcode.

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14
Q

What is API gateway?

A

A fully managed service that makes it easy for developers to publish, maintain, monitor, and secure APIs at any scale. A doorway into your aws environment. Typically used to communicate to Lambda functions.

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15
Q

True or False. API gateway can expose HTTPS endpoints to define a RESTful API.

A

True.

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16
Q

True or False. API gateway is limited to sending different targets to only one API endpoint.

A

False. It can send each API endpoint to a different target.

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17
Q

True or False. With API caching, you can reduce the number of calls made to your endpoint and also improve the latency of requests to your API.

A

True. When enabled, API Gatewaycaches response from your endpoint fro a specified time-to-live (TTL) period, in seconds. API gateway then responds to the request by looking up the endpoint response from the cache instead of making a request to your endpoint.

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18
Q

What is CORS and what is a workaround for?

A
  • Cross-origin resource sharing is a mechanism that allows restricted resources on a web page to be requested from another domain outside the domain from which the first resource was served.
  • It is a workaround for the same-origin policy. This policy is enforced by browsers to prevent cross-site scripting attacks.
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19
Q

What do you need to do if you see error “Origin policy cannot be read at the remote resource?”?

A

You need to enable CORS (cross-origin resource sharing) on API gateway.

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20
Q

What is Kinesis?

A

Platform on AWS to send all your streaming data. It makes it easy to load and analyze streaming data.

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21
Q

What are the three different types of Kinesis?

A
  1. Streams
  2. Firehose
  3. Analytics
22
Q

What is Kinesis Streams?

A

Data Producers stream data to Kinesis Streams for 24 hours to 7 days of retention. Each data stored is considered a shard. The data stored in the shard is available to consumers to analyze the data in the shard. Once analyzed, it can be stored in several AWS products that are accessible via EC2.

23
Q

What is Kinesis Firehose?

A

Kinesis Firehose does not have persistent storage. Optional to have Lambda functions that run code when the data is entered into the firehose. Can be stored in S3 / ElasticSearch.

24
Q

What is Kinesis Analytics?

A

Works with both Kinesis firehose / streams and analyzes the data provided. It then can store that data in s3, redshift or elastic search cluster.

25
Q

What is Web Identity Federation?

A

Gives your users access to AWS resources after they have successfully authenticated with a web-based identity provider like Amazon, Facebook, Google. Following successful authentication, the user receives an authentication code from the Web ID provider, which they can trade for temporary AWS security credentials.

26
Q

What is Cognito?

A

Acts as an identity broker between your application and web ID providers, so you don’t have to write additional code. Recommended for all mobile application services. It essentially brokers between the app and Facebook/Google to provide temporary credentials that map to an IAM role allowing access to the required resources.

27
Q

What are Cognito User Pools?

A

User directories used to manage sign-up and sign-in functionality for mobile and web applications. Broker between an identity provider and AWS. Successful authentication generates a JSON Web Token (JWT).

28
Q

What are Cognito Identity Pools?

A

Identity Pools enable temporary AWS credentials to access AWS services like s3/DyanmoDB

29
Q

True or False. Cognito tracks the association between user identity and the various different devices they sign-in from.

A

True.

30
Q

What is the difference between a user pool and an identity pool?

A

A user pool is user-based, handles things like user registration, authentication, and account recovery.

Identity pools authorize access to your AWS resources.

31
Q

Amazon SWF (Simple Workflow Service) is designed to help users ________.

  • Manage user identification and authorization
  • Coordinate synchronous and asynchronous tasks
  • Secure their VPCs
  • Store file-based objects
A

Coordinate synchronous and asynchronous tasks.

Similar to SQS, SWF manages queues of work, however, unlike SQS it can have out-of-band parallel and sequential task to be completed by humans and non-AWS services.

32
Q

True or False. Amazon SWF restricts me to the use of specific programming languages.

A

False. While there are a limited range of SDKs available for SWF, AWS provides an HTTP based API which allows you to interact using any language as long as you phrase the interactions in HTTP requests.

33
Q

True or False. Amazon SWF ensures that a task is assigned only once and is never duplicated.

A

True. One time only completion is a key feature of SWF. At one time this was a key distinction from SQS, however with SQS FiFo queues, this is no longer a distinguishing feature.

34
Q

True or False. Amazon’s SQS service guarantees a message will be delivered at least once.

A

True.

35
Q

True or False. AWS Glue is a fully managed extract, transform, and load (ETL) service that makes it easy for customers to prepare and load their data for analytics.

A

True.

36
Q

What is AWS Batch?

A

AWS Batch is used for running large numbers of batch computing jobs on AWS. AWS Batch dynamically provisions the EC2 instances. This is not a good solution for ad-hoc use cases where you just need to run a single script a few times a week.

37
Q

What is AWS CloudFormation?

A

AWS CloudFormation is used for launching infrastructure. You can use scripts with AWS CloudFormation but its more about running scripts related to infrastructure provisioning.

38
Q

What is IAM?

A

Manage users and level of access to aws console.

39
Q

True or False. SWF has a retention period of up to 14 days; with SQS, workflow executions can last up to a year.

A

False. SQS has a retention period of up to 14 days; with SWF, workflow executions can last up to a year.

40
Q

True or False. SWF presents a task-oriented API, whereas SQS offers a message-oriented API.

A

True.

41
Q

True or False. SWF ensures that the task is assigned only once and never duplicated. SQS needs to handle duplicated messages and may also need to ensure that a message is processed only once.

A

True.

42
Q

True or False. SQS keeps track of all the tasks and events in an application. SWF you need to implement your own application-level tracking especially if your application uses multiple queues

A

False. SWF keeps track of all the tasks and events in an application. SQS you need to implement your own application-level tracking especially if your application uses multiple queues

43
Q

True or False. There is no need to make any changes as all environment variables are encrypted by default with AWS Lambda

A

False. When you deploy your Lambda function, all the environment variables you’ve specified are encrypted by default after, but not during, the deployment process. They are then decrypted automatically by AWS Lambda when the function is invoked. If you need to store sensitive information in an environment variable, you should encrypt that information before deploying your Lambda function. The Lambda console makes that easier for you by providing encryption helpers that leverage AWS Key Management Service to store that sensitive information as Ciphertext.

44
Q

True or False. You can only apply one IAM role to a Task Definition for ECS services.

A

True.

45
Q

True or False. With Fargate you can apply IAM roles at the container and task level, whereas with the EC2 launch type you can only apply at the task level.

A

False. With the EC2 launch type you can apply IAM roles at the container and task level, whereas with Fargate you can only apply at the task level.

46
Q

True or False. AWS recommends you use target tracking in place of step scaling for most use cases.

A

True.

47
Q

True or False. If you do not want to manage EC2 instances you must use the AWS Fargate launch type which is a serverless infrastructure managed by AWS. Fargate only supports container images hosted on Elastic Container Registry (ECR) or Docker Hub.

A

True

48
Q

True or False. CloudTrail is used for recording API calls (auditing) whereas CloudWatch is used for recording metrics (performance monitoring). CloudTrail can be deployed with a single trail that is applied to all regions.

A

True.

49
Q

True or False. CloudFront cannot expose static public addresses.

A

True.

50
Q

True or False. Amazon EMR is a web service that enables businesses, researchers, data analysts, and developers to easily and cost-effectively process vast amounts of data. EMR utilizes a hosted Hadoop framework running on Amazon EC2 and Amazon S3.

A

True.

51
Q

True or False. Elastic Transcoder is used for analyzing files.

A

False. Elastic Transcoder is used for converting media file formats not analyzing files.