You are a team lead for the development of an application that will be hosted in AWS. The application will consist of a front end that will allow users to upload files. Part of the application will consist of sending and processing of messages by a backend service. You have been told to reduce the cost for the backend service but also ensure efficiency. Which of the following would you consider in the implementation of the backend service? Choose 2 answers from the options given below.

Answer options:

A.Create an SQS queue to handle the processing of messages.
B.Create an SNS topics to handle the processing of messages.
C.Create a Lambda function to process the messages from the queue.
D.Create an EC2 Instance to process the messages from the queue.

Answer – A and C
The SQS queue can be used to handle the sending and receiving of messages. To reduce costs, you can use Lambda functions to process the messages. The below is also given in the AWS Documentation.
Using AWS Lambda with Amazon SQS
Attaching an Amazon SQS queue as an AWS Lambda event source is an easy way to process the queue’s content using a Lambda function. Lambda takes care of:
Automatically retrieving messages and directing them to the target Lambda function.
Deleting them once your Lambda function successfully completes.
Option B is incorrect since you should use SQS for the handling of messages. SNS has no persistence. Whichever consumer is present at the time of message arrival, get the message and the message is deleted. If no consumers available, then the message is lost.
Option D is incorrect since this would not be a cost-effective option.
For more information on working with SQS, please refer to the below URL-
https://docs.aws.amazon.com/lambda/latest/dg/with-sqs.html
Good Discussion on StackOverflow here- : https://stackoverflow.com/questions/13681213/what-is-the-difference-between-amazon-sns-and-amazon-sqs