Serverless Applications

Question 1

What is process of Event-Driven Architecture in Serverless Enviornment?

Serverless Services and Event-Driven Architecture

Answer 1

1. User uploads file through static website
2. Serverless function processes file
3. Processed file is stored in bucket
4. Notification sent using SNS & email
5. Function processes message & stores information in database

Question 2

What are features of Serverless Services?

Serverless Services and Event-Driven Architecture

Answer 2

• No instances to manage
• No need to provision hardware
• No management of OS or software
• Capacity provisioning & patching handled automatically
• Provides automatic scaling & high availability
• Very cheap

Question 3

What is AWS Lambda?

AWS Lambda

Answer 3

Event-driven serverless compute service for running code w/out having to provision or manage server

Question 4

What is Lambda process?

AWS Lambda

Answer 4

• Developer uploads some code
• Event occurs. Can be:
  
  • CLI
  • API
  • SDK
  • Trigger
• Code executed

Question 5

What are features of Lambda?

AWS Lambda

Answer 5

• Executes code only when needed & scales automatically
• Only pay for compute time used (not when code is not running)
• Benefits
  
  • No servers to manage
  • Continious scaling
  • Millisecond billing
  • Integrates w/ other most other AWS service

Question 6

What are Primary use cases for Lambda?

Answer 6

• Data processing
• Real-time file processing
• Real-time stream processing
• Build serverless backends for web, mobile, IOT, & 3rd party API requests

Question 7

How can you invoke Lambda functions w/ Synchronous?

AWS Lambda

Answer 7

• CLI, SDK, API Gateway
• Wait for function to process event & return response
• Error handling happens client side (retries, exponential backoff, etc.)

Question 8

How can you invoke Lambda functions w/ Asynchronous?

AWS Lambda

Answer 8

• S3, SNS, CloudWatch Events, etc . . .
• Event is queued for processing & response is returned immediately
• Lambda retries up to 3 times
• Processing must be idempotent (due to retries)

Question 9

How can you invoke Lambda functions w/ Event Source Mapping?

AWS Lambda

Answer 9

• SQS, Kinesis Data Stream, DynamoDB Streams
• Lambda does polling (polls source)
• Records processed in order (except for SQS standard)

Question 10

True or False

SQS can also trigger Lambda

AWS Lambda

Answer 10

TRUE

Question 11

What are Lambda Function Concurrency Rules?

AWS Lambda

Answer 11

• Additional functions are initalized up to burst or account limit
• If concurrency limit is exceeded:
  
  • throttling occurs w/ error Rate exceeded
  • 429: TooMany Requests Exception

Question 12

What is Simple Queue Service (SQS)?

Application Integration Services Overview

Answer 12

Message queue; store & forward patterns

Ex: Building distributed/decoupled applications

Question 13

What is Simple Notification Service (SNS)?

Application Integration Services Overview

Answer 13

Set up, operate, & send notifications from cloud

Ex: Send email notification when CloudWatch alarm is triggered

Question 14

What are Step Functions?

Application Integration Services Overview

Answer 14

Out-of-box coordination of AWS service components w/ visual workflow

Ex: Order processing workflow

Question 15

What is Simple Workflow Service?

Application Integration Services Overview

Answer 15

Need to support external processes or specialized execution logic

Ex: Human-enabled workflows like an order fulfillment system or for procedural requests
Note: AWS recommends that for new applications customers consider Step Functions instead of SWF

Question 16

What is Amazon MQ?

Application Integration Services Overview

Answer 16

Message broker service for:
- Active MQ
- RabbitMQ

Ex: Need message queue that supports industry standard APIs & protocls; migrate queues to AWS

Question 17

What is Amazon Kinesis?

Application Integration Services Overview

Answer 17

Collect, process, & analyze streaming data

Ex: Collect data from IoT devices for later processing

Question 18

Describe features of Kinesis

Application Integration Services Overview

Answer 18

• Consumers pull data
• As many consumers as you need
• Routes related records to same record processor
• Multiple applications can access stream concurrently
• Ordering at shard level
• Can consume records in correct order at later time
• Must provision throughput

Question 19

Describe features of Amazon SQS

Application Integration Services Overview

Answer 19

• Consumers pull data
• Data deleted after being consumed
• Can have as many workers (consumers) as you need
• No ordering guarentee (except w/ FIFO queues)
• Provides messaging semantics
• Individual message delay
• Dynamically scales

Question 20

Describe features of SNS

Application Integration Services Overview

Answer 20

• Push data to many suscribers
• Publisher / subscriber model
• Integrates w/ SQS for fan-out architecture pattern
• Up to 10,000,000 subscribers
• Up to 100,000 topics
• Data IS NOT persisted
• No need to provision throughput

Question 21

What are features of Standard Queues?

SQS Queues

Answer 21

• Unlimited Throughput - support nearly unlimited number of transactions per second (TPS) per API action
• Best-Effort Ordering - Sometimes, messages might be delivered in order from which they were sent
• At-Least-Once Delivery - Message delivered at least once, but occasionally more than one copy of message is delivered

Question 22

What are features of FIFO Queues?

SQS Queues

Answer 22

• High Throughput - support up to 300 messages per second.
  
  • When 10 messages are batch per operation (maximum), can support up to 3,000 messages per second
• First-In-First-Out Delivery - Order which messages are sent & received strictly preserved
• Exactly-Once Processing - Message delivered once & remains available until consumer processes & deletes it.
  
  • No duplicates go in queue

Question 23

What are other features of FIFO Queues?

SQS Queues

Answer 23

• Require Message Group ID * & Message Deduplication ID paramters to be added to messages

Question 24

What is Message Group ID?

SQS Queues

Answer 24

Tag that specifies message belongs to specific message group Messages that belong to same message group are guaranteed to be processed in FIFO manner

Question 25

What is **Message Deduplication ID**? ## Footnote **SQS Queues**

Answer 25

Token used for deduplication of messages w/in deduplication interval

Question 26

What is **SQS - Dead Letter Queue**? ## Footnote **SQS Queues**

Answer 26

- Main task - handling message failure - Lets you set aside & isolate message that can't be processed correctly to determine why their processing didn't succeed - Not Queue Type: **Standard** or **FIFO** queue that has been specified as dead-letter queue in configuration of **another** standard or FIFO queue.

Question 27

What are settings of **Dead Letter Queues**? ## Footnote **SQS Queues**

Answer 27

- Enable Redrive Policy - Specify queue to use as dead-letter queue - Specify maximum receives before message is sent to dead-letter queue

Question 28

What is **Long Polling**? ## Footnote **SQS Queues**

Answer 28

- Way to retrieve messages from SQS queues - waits for messages to arrive - can lower costs - can be enabled at queue level or at API level using **WaitTimeSeconds** - In effect when Receive Message Wait Time is value greater than **0 seconds** up to **20 seconds**

Question 29

What is **Short Polling**? ## Footnote **SQS Queues**

Answer 29

Returns immediately (even is message queue is empty)

Question 30

What does an **Event Producer** do? ## Footnote **Amazon SNS**

Answer 30

Sends one message to SNS topic

Question 31

# **True or False** Does each subscriber get all messages? ## Footnote **Amazon SNS**

Answer 31

True

Question 32

# **True or False** Many suscribers listen for notifications

Answer 32

True

Question 33

What are features of Amazon SNS? ## Footnote **Amazon SNS**

Answer 33

- Highly available, durable, secure, fully managed pub/sub messaging service - Provides topics for high-throughout, push-based, many-to-many messaging - Publisher systems can fan out messages to large number of suscriber endpoints - Multiple recipients can be grouped using Topics - One topic can support deliveries to multiple endpoint types - Simple APIs & easy integration w/ applications - Flexible message delivery over multiple transport protocols

Question 34

What are Amazon SNS subscriber endpoints? ## Footnote **Amazon SNS**

Answer 34

- SQS queues - Lambda functions - HTTP/S webhooks - Mobile push - SMS - Email

Question 35

What is a **Topic**? ## Footnote **Amazon SNS**

Answer 35

*Access Point* for allowing recipients to dynamically suscribe for identical copies of same notification

Question 36

What are **AWS Step Functions**? ## Footnote **Amazon SNS**

Answer 36

Used to build distributed applications as series of steps in visual workflow - Quickly build & run state machines to execute steps of your application

Question 36

What are features of **SNS** + **SQS Fan-Out** ## Footnote **Amazon SNS**

Answer 36

- You can suscribe many SQS queues to SNS topic - SQS manages subscription & any necessary permissions - When you publish message to topic, SNS sends message to every subscribed queue

Question 37

How do AWS Step Functions work? ## Footnote **Amazon SNS**

Answer 37

1. Define steps of your workflow in **JSON-based Amazon States Language** - visual console automatically graphs each step in order of execution 2. Start execution to visualize & verify application steps are working. - **Operates & scales** steps of application & underlying compute for you to help ensure your application executes reliably under increasing demand

Question 38

What is **API Gateway**? ## Footnote **Amazon SNS**

Answer 38

Used for creating, publishing, maintaining, monitoring, & securing REST, HTTP, & WebSocket APIs at any scale.

Question 39

What are API Gateway Deployment Types & Their Benefits? ## Footnote **Amazon SNS**

Answer 39

- **Edge-Optimized Endpoint** - Reduced latency for requests from around world - **Regional Endpoint**: - Reduced latency for requests that originate in same region - Can also configure your own CDN & protect WAF - **Private Endpoint** - Securlty expose REST APIs only to other services w/in VPC or connect via Direct Connect

Question 40

What are **API Gateway Integration** Types? ## Footnote **Amazon SNS**

Answer 40

- **Lambda function** - Lambda proxy integration - Lambda custom integration - **HTTP Endpoint** - HTTP proxy integration - HTTP custom integration - **AWS Service Action** - Only with **non-proxy type** only

Question 41

How does **API Gateway - Caching** work? ## Footnote **Amazon SNS**

Answer 41

- Add caching to API calls by provising an Amazon API Gateway cache & specifying its size in gigabytes - Allows you to cache endpoint's response - Caching can reduce number of calls to backend & improve latency of requests to API

Question 42

What features does **API Gateway - Throttling** have? ## Footnote **Amazon SNS**

Answer 42

- Sets limit on steady-state rate & burst of request submissions against all APIs in your account - Limits: - Default API Gateway limits steady-state request rate to 10K requests per second - Maximum concurrent requests is 5K requests across all APIs w/in AWS account. - If you go over 10K requests per second or 5K concurrent requests you'll receive *429 Too Many Requests* error response - Upon catching such exceptions, client can resubmit failed requests in way that is rate limiting, while complying w/ API Gateway throttling limits.