Exam AWS Certified Developer Associate topic 1 question 15 discussion

A and B are for read problem, nor for write. C its not possible because enhanced fanout its for kinesis D is the most probably

Read replicas are for read... transactions means that something have to be written. There is no such thing of fanout for lambda. This lead to D. Because we've limited the number of concurrent lambdas to be lower than the number of connections, the system will run with no problems

"enhanced fanout" is only for Kinesis-Lambda integration, not for SQS. Therefore answer D is best

D) Correct - By adding an SQS queue between the point-of-sale devices and the Lambda function, you can handle spikes in transaction volume without overwhelming the Lambda function or the RDS database. Limiting the concurrency of the Lambda function ensures that the number of simultaneous connections to the database does not exceed what the RDS instance can handle.

B is seamly correct

A&B are out because the aplpication writes to the DB, therefore read replicas do not help. C ist out because enahced fan out is a kinesis feature D solves the issue. Setting the concurrency limit to the number of database connections ensures that all running lambdas can successfuly write to the database.

B. auto scalling is cost effective.

option c Using an Amazon SQS queue to buffer transactions and then invoking the Lambda function can help in managing the varying transaction load. Turning on enhanced fanout for the Lambda function allows it to scale more effectively by processing records in parallel.

Option C leverages the scalability of SQS and enhanced fanout for Lambda, making it the most cost-effective and suitable choice for handling varying transaction loads efficiently.

C is correct because you are turning Kinesis enhanced fan out FORFORFOR Lambda not Lambda fanout itself. The scenario is exactly stating this. https://aws.amazon.com/about-aws/whats-new/2018/11/aws-lambda-supports-kinesis-data-streams-enhanced-fan-out-and-http2/

reserved concurrency is not cost effectively, D is not correct

It can't be C. Enhanced fan-out is a feature of Amazon Kinesis Data Streams, not SQS. Enhanced fan-out allows multiple consumers to receive data from a Kinesis data stream concurrently. D is the most probable

Again, tricky question! I was for B but if we think about that, it is written "stores the transactions in Amazon RDS" and the B option is only about read replicas. So I changed my mind and now I will go for D as well. It makes sense to create a Queue before process the transactions and publish messages to the SQS Queue and attach a lambda function to perform the transaction. Also, set the reserved concurrency (max number of parallel invocations for a function) less than to the number of DB connections is a brilliant idea to avoid concurrency issues with the function.

keyword is "increase the elasticity of the system MOST cost-effectively" we can find relative keyword auth-scaling

Should be d

transactions -> need write function. A, B only for read function -> out C: enhanced fan-out is feature of Kinesis. Lambda does support it but only with Kinesis, not with SQS -> out D make sense since SQS + Lambda is a pattern, plus setting reserved concurrency limit makes sense

This approach uses an Amazon SQS queue to decouple the point-of-sale devices from the centralized system, allowing for better scalability and reliability. The queue can handle large volumes of transactions during peak periods and ensure that the transactions are processed in a timely manner by invoking the Lambda function. Using enhanced fanout for the Lambda function can further increase its elasticity by allowing multiple instances to process messages concurrently. This is the most cost-effective approach as it doesn't require any changes to the existing RDS database or the use of expensive Aurora Auto Scaling.