Decoupling Workflows

Question 1

What can the SQS delivery delay be set to? What’s the default?

Answer 1

• 0-15min
• Default 0

Question 2

How large can an SQS message be?

Answer 2

256kb

Question 3

How is SQS encrypted?

Answer 3

• Encrypted in transit by default
• Must enable at-rest encryption.

Question 4

How long do SQS messages live by default? Whats the min and max?

Answer 4

• 4 days default
• Min 1 minute
• Max 14 days

Question 5

What is long and short polling? Which should you favor?

Answer 5

• Short polling polls often for short periods.
• Long polling remains connected longer.
• Favor long polling generally.

Question 6

What is Queue Depth used for?

Answer 6

• Queue depth can trigger autoscaling if there is a backup in messages.

Question 7

What is the visibility Timeout? What is it for?

Answer 7

• Its the amount of time after a message is downloaded that a message is locked from being read by other consumers.
• Ensures proper handling of messages

Question 8

What is the default SQS visibility Timeout?

Answer 8

30 Seconds

Question 9

What’s more efficient? Long polling or short polling? What might this cause?

Answer 9

• Long polling
• Burning through API calls
• Higher cost

Question 10

What are the restrictions on the contents of SQS messages?

Answer 10

None

Question 11

What’s a dead-letter queue?

Answer 11

• Its just an SQS Queue
• Allows us to move messages to another queue temporarily after a number of retries

Question 12

What attributes make a Dead Letter Queue?

Answer 12

• Enabling the DLQ to receive undeliverable messages
• Entering the ARN of the queue to receive dead messages from

Question 13

What can you do with problematic SQS messages?

Answer 13

Send them to an SQS Desd-letter Queue

Question 14

how can you know if a DLQ is filling up?

Answer 14

Use Cloudwatch to create an alarm and SNS to notify.

Question 15

What can you do if an SNS message fails to deliver?

Answer 15

You can send it to a dead letter queue

Question 16

What is the rate limit for FIFO queues?

Answer 16

300 per second

Question 17

Can messages arrive out of order?

Answer 17

Yes. It’s “best effort” ordering

Question 18

Whats the limit of message rate with SQS?

Answer 18

Nearly unlimited

Question 19

Can an SQS message be received more than once by a consumer?

Answer 19

• Standard? Yes
• Fifo? No

Question 20

Does FIFO cost more or the same as Standard SQS Queues?

Answer 20

It costs more.

Question 21

Exam says “ordering” and “SQS” you say…

Answer 21

FIFO

Question 22

What is a message “fan out”

Answer 22

• Using SQS and SNS
• you send an SNS to SQS which pushes it out

Question 23

How large can an SNS message be?

Answer 23

256kb

Question 24

Can an SNS topic be FIFO?

Answer 24

Yes, but only subscriber is SQS.

Question 25

How can you limit who publishes into SNS topics

Answer 25

Policies!

Question 26

What security can you apply to API Gateway?

Answer 26

You can assign a WAF to API Gateway

Question 27

Why use API Gateway?

Answer 27

• Security
• Stop potential abuse of your apps
• Ease of use

Question 28

What is the difference between Amazon MQ and Amazon SQS

Answer 28

• Amazon MQ uses industry-standard APIs and Protocols
• It’s managed Apache MQ

Question 29

What’s the maximum number of standard SQS messages that can be in a queue? FIFO Messages?

Answer 29

• 120,000 in-flight messages for standard
• 20,000 in-flight messages for FIFO