Decoupling Workflows Flashcards
What can the SQS delivery delay be set to? What’s the default?
- 0-15min
- Default 0
How large can an SQS message be?
256kb
How is SQS encrypted?
- Encrypted in transit by default
- Must enable at-rest encryption.
How long do SQS messages live by default? Whats the min and max?
- 4 days default
- Min 1 minute
- Max 14 days
What is long and short polling? Which should you favor?
- Short polling polls often for short periods.
- Long polling remains connected longer.
- Favor long polling generally.
What is Queue Depth used for?
- Queue depth can trigger autoscaling if there is a backup in messages.
What is the visibility Timeout? What is it for?
- 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
What is the default SQS visibility Timeout?
30 Seconds
What’s more efficient? Long polling or short polling? What might this cause?
- Long polling
- Burning through API calls
- Higher cost
What are the restrictions on the contents of SQS messages?
None
What’s a dead-letter queue?
- Its just an SQS Queue
- Allows us to move messages to another queue temporarily after a number of retries
What attributes make a Dead Letter Queue?
- Enabling the DLQ to receive undeliverable messages
- Entering the ARN of the queue to receive dead messages from
What can you do with problematic SQS messages?
Send them to an SQS Desd-letter Queue
how can you know if a DLQ is filling up?
Use Cloudwatch to create an alarm and SNS to notify.
What can you do if an SNS message fails to deliver?
You can send it to a dead letter queue
What is the rate limit for FIFO queues?
300 per second
Can messages arrive out of order?
Yes. It’s “best effort” ordering
Whats the limit of message rate with SQS?
Nearly unlimited
Can an SQS message be received more than once by a consumer?
- Standard? Yes
- Fifo? No
Does FIFO cost more or the same as Standard SQS Queues?
It costs more.
Exam says “ordering” and “SQS” you say…
FIFO
What is a message “fan out”
- Using SQS and SNS
- you send an SNS to SQS which pushes it out
How large can an SNS message be?
256kb
Can an SNS topic be FIFO?
Yes, but only subscriber is SQS.
How can you limit who publishes into SNS topics
Policies!
What security can you apply to API Gateway?
You can assign a WAF to API Gateway
Why use API Gateway?
- Security
- Stop potential abuse of your apps
- Ease of use
What is the difference between Amazon MQ and Amazon SQS
- Amazon MQ uses industry-standard APIs and Protocols
- It’s managed Apache MQ
What’s the maximum number of standard SQS messages that can be in a queue? FIFO Messages?
- 120,000 in-flight messages for standard
- 20,000 in-flight messages for FIFO
