Services

Question 1

What are Step Functions?

Answer 1

Step Functions allow you to visualize and test your serverless applications. Step Functions provide a graphical console to arrange and visualize the components of your application as a series of steps. This makes it simple to build and run multistep applications. Step Functions automatically triggers and tracks each step, and retries when there are errors, so you application executes in order and as expected. Step Functions logs the state of each step, so when things do go wrong, you can diagnose and debug problems quickly.

Question 2

What is X-Ray?

Answer 2

X-Ray is a service that collects data about requests that your application serves, and provides tools you can use to view, filter and gain insights into that data to identify issues and opportunities for optimization. For any traced request to your application, you can see detailed information not only about the request and response, but also about calls that your application makes to downstream AWS resources, microservices, databases and HTTP web APIs.

Question 3

How does the X-Ray architecture work?

Answer 3

You have your application, and you have the X-Ray SDK installed. The SDK then sends bits of information to the X-Ray daemon (can be installed on Linux, Windows, Mac OS X), It’s listening on UDP and takes the JSON it gets from the SDK and sends it to the X-Ray API. The API stores all the data and creates the visualization that you can see in the X-Ray console.

Question 4

What does the X-Ray SDK provide?

Answer 4

The X-Ray SDK provides:

Interceptors to add to your code to trace incoming HTTP requests.
Client handlers to instrument AWS SDK clients that your application uses to call other AWS services.
An HTTP client to use to instrument calls to other internal and external HTTP web services.

Question 5

What services does X-Ray integrate with?

Answer 5

X-Ray integrates with Elastic Load Balancing, Lambda, API Gateway, EC2 and Elastic Beanstalk.

Question 6

What languages are supported by X-Ray?

Answer 6

Java, Go, Node.js, Python, Ruby, .Net

Question 7

What is streaming data?

Answer 7

Streaming data is data that is generate continously by thousands of data sources, which typically send in the data records simultaneously, and in small sizes (order of kilobytes).

Question 8

What are some examples of streaming data?

Answer 8

Purchases from online stores. 
Stock prices. 
Game data (as the gamer plays).
Social network data.
Geospatial data (Uber).
iOT sensor data.

Question 9

What is Kinesis?

Answer 9

Kinesis is a platform on AWS to send your streaming data to. Kinesis makes it easy to load and analyze streaming data, and also providing the ability for you to build your own custom applications for you business needs.

Question 10

What are the core Kinesis services?

Answer 10

Kinesis Streams, Kinesis Firehose and Kinesis Analytics.

Question 11

What is Kinesis Streams?

Answer 11

Imagine you have several data producers (like EC2 instances, cell phones, laptops, etc.) that are sending data to a Kinesis Stream. Kinesis Streams store this data, by default for 24 hours, but also up to 7 days.

The data is stored in shards. The data is then sent to a fleet of EC2 instances (consumers) which take your data and turn it into something useful (perform calculations, etc.). Once they’ve done their useful thing, they can send the data to be stored in DynamoDB, S3, EMR or Redshift.

Question 12

What are shards?

Answer 12

Kinesis Streams consist of shards. Shards basically has two purposes: 1) a certain amount of capacity/throughput and 2) an ordered list of messages.

Question 13

What is the data capacity of your Kinesis Stream?

Answer 13

The data capacity of your stream is a function of the number of shards that you specify for the stream. The total capacity of the stream is the sum of the capacities of its shards.

Question 14

What is Kinesis Firehose?

Answer 14

Just as with Kinesis Streams, you have producers sending data to your Kinesis Firehose. But unlike Streams, you don’t have shards (this is automated for you). You also don’t have to worry about consumers going in and analyzing your data (you can analyze the data using Lambda in real time). Once the data has been analyzed you can send it directly to S3 (analyzing is optional). There’s not data retention window, when you send data to Kinesis Firehose, it’s either analyzed using Lambda, or sent directly to S3, Redshift, Elasticsearch Cluster.

Question 15

What is Kinesis Analytics?

Answer 15

Kinesis Analytics allows you to run SQL queries on the data as it exists in your Stream or Firehose and then you can use that SQL query to store that data in S3, Redshift or Elasticsearch cluster. So it’s a way of analyzing data inside Kinesis using SQl type querying language.

Question 16

How can you define a Kinesis data stream?

Answer 16

It is a set of shards. A shard is a sequence of data records in a stream, each data record has a unique sequence number.

Question 17

What is Kinesis Stream consumer?

Answer 17

A consumer is an EC2 instance that is consuming data of your stream. On your consumer instances, you have the Kinesis Client Library running. This tracks the number of shards in your stream and discovers new shards when you reshard.

Question 18

When using Kinesis Stream, when should you scale out your consumers?

Answer 18

It’s fine if the number of shards exceeds the number of instances. Don’t think that just because you reshard, that you need to add more instances. Instead, CPU utilization is what should drive the quantity of consumer instances you have, NOT the number of shards in your Kinesis Stream. Best practice would be to use an auto scaling group, and base scaling decisions on CPU load of your consumers.

Question 19

What does the Kinesis Client Library do?

Answer 19

The Kinesis Client Library running on your consumers creates a record processor for each shard that is being consumed by your instance. If you increase the number of shards, the KCL will add more record processors on your consumers, and it will split them equally between the number of consumers that you have.

Question 20

What is Elastic Beanstalk?

Answer 20

Elastic Beanstalk is a service for deploying and scaling web applications developed in many popular languages: Java, .NET, PHP, Node.js, Python, Ruby, Go and Docker onto widely used application server platforms like Apache Tomcat, Nginx, Passenger, Puma and IIS.

Developers can focus on writing code and don’t need to worry about any of the underlying infrastructure needed to run the application.

Question 21

How do you use Elastic Beanstalk?

Answer 21

You upload the code and Elastic Beanstalk will handle deployment, capacity provisioning, load balancing, auto-scaling and application health.

You retain full control of the underlying AWS resources powering your application and you pay only for the AWS resources required to store and run your applications (e.g. EC2 instances and S3 buckets).

Question 22

What are the different Elastic Beanstalk deployment policies?

Answer 22

Elastic Beanstalk supports several options for processing deployments:

All at once
Rolling
Rolling with additional batch
Immutable

Question 23

What is an All at Once deployment policy?

Answer 23

All at Once deployment updates:

• Deploys the new version to all instances simultaneously
• All of your instances are out of service while the deployment takes place.
• You will experience an outage while the deployment is taking place, i.e. it’s not ideal for mission-critical production systems.
• If the update fails, you need to roll back the changes by re-deploying the original version to all your instances.

Question 24

What is a rolling deployment policy?

Answer 24

Rolling deployment updates:

• Deploys the new version in batches
• Each batch of instances is taken out of service while the deployment takes place.
• Your environment capacity will be reduced by the number of instances in a batch while the deployment takes place.
• Not ideal for performance sensitive systems.
• If the update fails, you need to perform an additional rolling update to roll back the changes.

Question 25

What is a rolling with additional batch deployment policy?

Answer 25

Rolling with additional batch deployment updates:

• Launches an additional batch of instances.
• Deploys the new version in batches.
• Maintains full capacity during the deployment process.
• If the update fails, you need to perform an additional rolling update to roll back the changes.

Question 26

What is the immutable deployment policy?

Answer 26

Immutable deployment updates:

• Deploys the new version to a fresh group of instances in their own new autoscaling group.
• When the new instances pass their health checks, they are moved to your existing auto scaling group; and finally, the old instances are terminated.
• Maintains full capacity during the deployment process
• The impact of a failed update is far less, and the rollback process requires only terminating the new auto scaling group
• Preferred option for mission critical production systems.

Question 27

How can you customize your Elastic Beanstalk environment?

Answer 27

You can customize your Elastic Beanstalk environment using configuration files. E.g., you can define packages to install, create Linux users and groups, run shell commands, specify services to enable or configure your load balancer, etc.

Question 28

What formats can Elastic Beanstalk configuration files be in and where must they be saved?

Answer 28

Elastic Beanstalk configuration files are written in YAML or JSON format. They can have any filename, but must have a .config extension and be saved inside a folder called .ebextensions

Question 29

Where is the .ebextensions folder?

Answer 29

The .ebextensions folder must be included in the top-level directory of your application source code bundle. This means that the configuration files can be placed under source control along with the rest of your application code.

Question 30

What are the two supported ways of intergating an RDS database with your Beanstalk environment?

Answer 30

You can:

1) launch the RDS instance from within the Elastic Beanstalk console, which means the RDS instance is created within your Elastic Beanstalk environment, this is a good option for test/dev deployments. However, this may not be ideal for production environments because it means the lifecycle of your database is tied to the lifecycle of your application environment. If you terminate the environment, the database instance will be terminated too.
2) launch the RDS instance outside of Elastic Beanstalk. This way, you are decoupling the RDS instance from your environment, which is preferred for production environments. This options gives you more flexibility, because it allows you to connect multiple environments to the same database, provides a wider choice of database types, and allows you to tear down your application environment without affecting the database instance.

Question 31

How do you allow EC2 instances in your Elastic Beanstalk environment to connect to an outside database?

Answer 31

There are two additional configuration steps required:

1) An additional security group must be added to your environment’s auto scaling group.
2) You’ll need to provide connection string configuration information to your application servers (endpoint, password)

Question 32

What is an Application Load Balancer?

Answer 32

Application Load Balancers are best suited for load balancing of HTTP and HTTPS traffic. They operate at layer 7 and are application-aware. They are intelligent, and you can create advanced request routing, sending specified requests to specific web servers.

Question 33

What is a Network Load Balancer?

Answer 33

Network Load Balancers are best suited for load balancing of TCP traffic where extreme performance is required. Operating at the connection level (layer 4), network load balancers are capable of handling millions of requests per second, while maintaining ultra-low latencies. Used for extreme performance!

Question 34

What is a Classic Load Balancer?

Answer 34

Classic Load Balancers are the legacy Elastic Load Balancers. You can load the HTTP/HTTPS applications and use layer-7 specific features, such as X-Forwarded-For and sticky sessions. You can also use strict layer 4 load balancing for applications that rely purely on the TCP protocol.

Question 35

If your classic load balancer returns a 504 error, what could the problem be?

Answer 35

If your application stops responding, the classic load balancer returns with a 504 error. This means that the application is having issues. This could be either at the web server layer or at the database layer.

Question 36

What’s the max execution time for Lambda?

Answer 36

900 seconds. 15 min.

Question 37

What’s the max memory for a Lambda function?

Answer 37

3 GB.