[DEVELOPER] Advanced SQS + SNS

Question 1

Explain how SQS Extended Client works

Answer 1

Question 2

Say you want to send a message through SQS of 1GB. How might you do this?

Answer 2

SQS Extended Client

Question 3

Why is SQS Long Polling preferable to Short Polling?

Answer 3

increases efficiency and latency of the application by decreasing number of API calls made to SQS

Question 4

What are the configuration limits for wait time for SQS Long Polling?

Answer 4

1-20 seconds, (but 20 seconds is preferred)

Question 5

What is the name API-level field for configuring SQS Long Polling?

Answer 5

RecieveMessageWaitTimeSeconds

Question 6

What does the SQS API call PurgeQueue do?

Answer 6

delete all messages in the queue

Question 7

Suppose you are using an SQS/SNS fan-out pattern for an ordering service, but one of your SQS queues should only receive messages that are of the “placed” state. There are multiple SQS queues and you expect not all of your incoming messages will have a “placed” state. How can you implement this functionality?

Answer 7

Use SNS Message Filtering (aka fitler policies)

Question 8

Suppose you want to send one S3 Event to many SQS queues. How can you do this in S3?

Answer 8

You cant do it in S3, because for each (event type, prefix) you can only have 1 S3 event rule

Instead Use SNS/SQS Fan-out (configure events to SNS)

Question 9

Suppose you want to configure your messaging system to have ordering, deduplication, and fan-out. How can you accomplish this?

Answer 9

SNS FIFO Topic AND SQS FIFO Queue

Question 10

Can Lambda subscribe to an SNS FIFO Topic?

Answer 10

NO

only SQS FIFO can subscribe to an SNS FIFO topic

Question 11

What are the two methods for SQS FIFO deduplication?

Answer 11

1. Explicit MessageDeduplicationID
2. Content-based Deduplication (a SHA-256 of the message body)

Question 12

Suppose you have an SQS queue in one account and an EC2 instance in another account that needs to poll from that SQS queue. How can you configure this to happen?

Answer 12

Apply an SQS Queue Policy on the queue to give ReceiveMessage permissions to the account with the EC2 instance

Question 13

Suppose you want to publish an S3 event notification to an SQS queue. You check the SQS queue but the messages are not showing up there. What might you need to do?

Answer 13

Configure an SQS Queue Policy on the queue to give SendMessage permissions to the S3 Bucket

Question 14

Suppose you want to send one S3 Event to many SQS queues. How can you do this?

Answer 14

Use SNS/SQS Fan-out (configure events to SNS)

S3 Event -> SNS -(fan out) -> SQS queues

Recall: for each (event type, prefix) you can only have 1 S3 event rule

Question 15

What is the name of the API Call you need to make to change the visibility timeout of an SQS queue?

Answer 15

ChangeMessageVisibility

Question 16

What is the name of the API call an SQS queue makes after successfully processing a message?

Answer 16

DeleteMessage

Question 17

What is primary purpose of the Partition Key when you execute a Put Record into Kinesis Data Sterams?

Answer 17

ensure ordering of similar records

Also records with the same parition key aer mapped to the same shard

Question 18

What is the name of the API call used to retrieve data from a specific shard in Kinesis Data Streams?

Answer 18

GetRecords (after first calling GetShardIterator to locate the starting point).

Question 19

In an SNS → SQS Fan-out setup, how do you prevent an SQS queue from receiving messages it doesn’t need?

Answer 19

Apply an SNS Filter Policy (or Message Filtering) to the SQS subscription, based on attributes in the SNS message.

Question 20

How does a developer prevent failed messages from being lost when an SQS consumer fails to process a message repeatedly?

Answer 20

Configure a Dead-Letter Queue on the SQS queue, specifying a maxReceiveCount (the maximum number of times a message can be received before it’s moved to the DLQ).

Question 21

What does DLQ stand for?

Answer 21

Dead Letter Queue

Question 22

What is the key difference between SNS and EventBridge?

Answer 22

SNS can only filter/route based on metadata

EventBridge can filter/route based on any field in the structured JSON body

Question 23

What AWS service is used to orchestrate complex, multi-step, stateful workflows involving multiple AWS services?

Answer 23

AWS Step Functions

Question 24

What is the language used to define a Step Function workflow (State Machine)?

Answer 24

Amazon States Language (or ASL)

Question 25

What are the primary features of Step Functions that simplifies code compared to a Lambda-only workflow?

Answer 25

- State management - Error handling - Retries - Sequencing

Question 26

What does **MQ** stand for | (as in Amazon MQ)

Answer 26

**M**essage **Q**ueue

Question 27

When should a developer choose Amazon MQ over SQS or SNS?

Answer 27

Only when an application **requires industry-standard messaging protocols** like JMS or AMQP (typically for a lift-and-shift of a legacy application).

Question 28

What two popular open-source message brokers does Amazon MQ support?

Answer 28

1. ActiveMQ 2. RabbitMQ

Question 29

What is the purpose of the **Visibility Timeout** in an SQS Standard queue?

Answer 29

The **amount of time that a message is hidden from other consumers after one consumer reads it**. This ensures that only one consumer processes a message at a time.

Question 30

How can a developer debug a problem where messages in a Standard SQS queue are being processed multiple times?

Answer 30

**The Visibility Timeout is too short**. The original consumer failed to delete the message before the timeout expired, making the message visible again to other consumers.

Question 31

How do you prevent an SQS message from being delivered more than once in a FIFO queue?

Answer 31

Use the `MessageDeduplicationId` parameter or **enable Content-Based Deduplication** on the queue.

Question 32

What are the two main API calls a developer uses for an SQS Consumer application?

Answer 32

`ReceiveMessage` (to get the message) and `DeleteMessage` (to confirm successful processing).

Question 33

If you want to use SQS to trigger a Lambda function, which polling setting must you configure, and why?

Answer 33

SQS uses a **Lambda Event Source Mapping** which uses **long polling** internally to minimize cost and latency for new messages.

Question 34

What are the four most common Endpoint Types (Protocols) that can subscribe to an SNS Topic?

Answer 34

1. SQS (for Fan-out/Decoupling), 2. Lambda (for serverless processing), 3. HTTP/S (for webhooks), 4. Email.

Question 35

How can you secure messages sent over an HTTP/S subscription to an external endpoint?

Answer 35

Enable **SSL/TLS** on the endpoint, and use the built-in raw message delivery feature if the message is too large or complex for the default SNS wrapping.

Question 36

How does a developer enable Server-Side Encryption (SSE) for an SNS Topic?

Answer 36

By specifying a KMS Customer Master Key (CMK) when creating or configuring the SNS Topic.

Question 37

A developer is writing a CloudFormation template for an SQS queue. They want the queue to only accept messages published from a specific SNS topic in the same account. Which resource property should be used?

Answer 37

The SQS queue's `QueuePolicy` resource property.