SNS

Question 1

What is SNS?

Answer 1

Amazon Simple Notification Service (SNS) is a highly available, durable, secure, fully managed pub/sub messaging service

Question 2

How many event receivers can you define on SNS?

Answer 2

A lot (10 000 000 per topic)

Question 3

What do the event subscriptors listen to?

Answer 3

To an SNS topic

Question 4

Who sends messages to an SNS topic?

Answer 4

The event publisher

Question 5

What messages will get an SNS event subscriber?

Answer 5

all the messages in the topic (can filter)

Question 6

How many topics can you define on SNS?

Answer 6

A lot (100 000)

Question 7

What are the possible SNS subscribers?

Answer 7

• SQS
• HTTP / HTTPS (with delivery retries – how many times)
• Lambda
• Emails
• SMS messages
• Mobile Notifications

Question 8

What services can send data directly to SNS?

Answer 8

Many AWS services can send data directly to SNS for notifications
• CloudWatch (for alarms)
• Auto Scaling Groups notifications
• Amazon S3 (on bucket events)
• CloudFormation (upon state changes => failed to build, etc)
• Etc…

Question 9

How can you publish to SNS within your AWS server

Answer 9

Using SDK or CLI:
• Create a topic
• Create a subscription (or many)
• Publish to the topic

Question 10

What can you use to publish to SNS for mobile apps SDK?

Answer 10

Direct Publish
o	Create a platform application
o	Create a platform endpoint
o	Publish to the platform endpoint
o	Works with Google GCM, Apple APNS, Amazon ADM…

Question 11

What is Fan Out?

Answer 11

• Push once in SNS, receive in all SQS queues that are subscribers
• Fully decoupled, no data loss

Question 12

How is encryption in SNS?

Answer 12

o In-flight encryption using HTTPS API (Enabled by default)
o At-rest encryption using KMS keys (Disabled by default)
o Client-side encryption if the client wants to perform encryption/decryption itself

Question 13

How is SNS access regulated?

Answer 13

• IAM policies to regulate access to the SNS API

- SNS Access Policies (similar to S3 bucket policies)

Question 14

What is useful for SNS Access Policies?

Answer 14

o Useful for cross-account access to SNS topics

o Useful for allowing other services (S3…) to write to an SNS topic

Question 15

What limitation is present in Fan Out pattern?

Answer 15

SNS cannot send messages to SQS FIFO queues (AWS limitation)

Question 16

What is a common case scenario for Fan Out pattern?

Answer 16

• For the same combination of: event type (e.g. object create) and prefix (e.g. images/) you can only have one S3 Event rule
• If you want to send the same S3 event to many SQS queues, use fan-out