SQS: Simple Queue Service Flashcards
What does Simple Queue Service provide?
Public, fully managed, highly available queues - standard or FIFO. It provides a mechanism for discrete resources to communicate in a decouple manner.
Which Zone does Simple Queue Service run in?
SQS runs in the AWS Public Zone.
How resilient is Simple Queue Service?
SQS is Region resilient.
What is the difference between Standard and FIFO queues in Simple Queue Service?
FIFO is guaranteed first in first out. FIFO queues guarantee exactly-once delivery.
Standard is best effort ordering. Standard queues guarantee at-least-once delivery.
What is the maximum message size in Simple Queue Service?
256KB. You can link to larger data in an S3 bucket (or some other data store).
How does Simple Queue Service implement fault tolerance?
By using a visibility timeout on messages. Messages are hidden for a period of time when a consumer receives them. The message will reappear unless that consumer finishes its processing and then explicitly deletes the message from the queue.
What is a dead letter queue in Simple Queue Service?
If a message fails to be deleted over and over again, it can be put in a dead letter queue for troubleshooting. Using a redrive policy, you can specify a dead letter queue to send a message to when its receiveCount on a message is greater than the maxReceiveCount. You can configure Alarms when messages arrive on a dead line queue.
Queue retention period calculations are based on the enqueue time to the original queue, so dead letter queues should have longer retention periods than regular queues.
How do Auto Scaling Groups integrate with Simple Queue Service?
By scaling in or out based on the length of a queue.
What is Simple Notification Service / Simple Queue Service fanout?
Subscribing multiple SQS queues to a single SNS Topic. When SNS sends a message to the topic, that message can then be added to each of the queues to allow for multiple tasks to be started based on a single event.
What is the maximum performance of a FIFO queue in Simple Queue Service?
3,000 messages per second with batching.
300 messages per second without batching.
How are you billed for Simple Queue Service?
Based on requests. A request can read 1-10 messages up to 64KB total.
What is the difference between short polling and long polling in Simple Queue Service?
Short polling returns results immediately. Long polling waits up to 20 seconds (waitTimeSeconds) if there are no messages on the queue and then return the messages that arrive in that window. Long polling uses fewer requests.
Can Simple Queue Service messages be encrypted at rest?
Yes, using KMS. They are already encrypted in transit.
How do you give cross-account access to a Simple Queue Service queue?
Using a Queue Policy (which is a type of Resource Policy).
What naming convention must a queue follow to be a valid FIFO queue?
It must have a .fifo suffix.
