I noticed Helen released this good DEV.to post on SNS and SQS and I happen to have a video of the same nature lying around and thought I'd upload it to provide an explanation from a different perspective.
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A little bit more about Message Services
The 4 most important services you need to know when it comes to Application Integration are the following:
SNS - PubSub (think pass along)
SQS - Queueing (think batch)
Kinesis - Real-time
SWF - Queuing but with people
For the Solution Architect Associate and Certificated Cloud Practitioner you really need to know the difference between SNS and SQS.
MKS - Amazon Managed Streaming for Kafka
Most companies in BigData who want to use real-time messaging systems tend to use Kafka. Luckily AWS has a managed service called MKS (Managed Kafka Service).
Kinesis
The use case for Kinesis has been really good for gaming where you need a simple streaming queue. There is a Solutions Architect Professional exam question which asks how you would ingest millions of events from IoT game devices to then insert into a database such as DynamoDB to update a scoreboard, and so Kinesis is what you would keep in mind.
At ExamPro we built our own real-time event tracking (think GoogleAnalytics) so we can accurately track and improve how people learn on our platform.
SNS - Amazon Simple Notification Service
SNS is commonly used for sending simple internal emails. So for example when someone sign-ups on ExamPro I use the AWS SDK to send a message to an SNS topic which then sends me a plain text email.
Another way we use SNS is to trigger webhooks in your application. So for example, let us say you have a web-app which needs to extract data out of a PDF so you need to use a PDFTK which you have to run in a custom runtime in a Lambda function because of legacy reasons. When that lambda has processed that pdf you want to notify your web-app to tell the user it's done. You can have Lambda tell SNS which will then send an HTTP request to an api endpoint (webhook) to your web-app which will then update the user that the pdf has finished processing.
SQS - Amazon Simple Queue Service
When we send out an email such as confirmation or reset password on ExamPro we use SQS to decouple email sending from our app so it doesn't cause the app to hang. ExamPro is a Rails app and so this gem called Shoryuken makes it really easy to start working with SQS will little knowledge.
Nobody I know uses this service. It's used by AWS I believe to help coordinate a sequence of tasks with people and services which makes sense for Amazon when they need to have humans put things into boxes and then ship those boxes.
There isn't even a new AWS icon. I've never been able to figure out how to access this service. It shows up on exams.
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