SAP-C02 · Question #524
A media storage application uploads user photos to Amazon S3 for processing by AWS Lambda functions. Application state is stored in Amazon DynamoDB tables. Users are reporting that some uploaded photo
The correct answer is B. Evaluate and adjust the WCUs for the DynamoDB tables. D. Add an Amazon Simple Queue Service (Amazon SQS) queue and reprocessing logic between. To address Lambda concurrency limits and DynamoDB write performance issues during simultaneous photo uploads, an SQS queue should be introduced between S3 and Lambda to buffer events and allow controlled processing, and the DynamoDB tables' Write Capacity Units (WCUs) should be e
Question
A media storage application uploads user photos to Amazon S3 for processing by AWS Lambda functions. Application state is stored in Amazon DynamoDB tables. Users are reporting that some uploaded photos are not being processed properly. The application developers trace the logs and find that Lambda is experiencing photo processing issues when thousands of users upload photos simultaneously. The issues are the result of Lambda concurrency limits and the performance of DynamoDB when data is saved. Which combination of actions should a solutions architect take to increase the performance and reliability of the application? (Choose two.)
Options
- AEvaluate and adjust the RCUs for the DynamoDB tables.
- BEvaluate and adjust the WCUs for the DynamoDB tables.
- CAdd an Amazon ElastiCache layer to increase the performance of Lambda functions.
- DAdd an Amazon Simple Queue Service (Amazon SQS) queue and reprocessing logic between
- EUse S3 Transfer Acceleration to provide lower latency to users.
How the community answered
(43 responses)- A14% (6)
- B51% (22)
- C9% (4)
- E26% (11)
Why each option
To address Lambda concurrency limits and DynamoDB write performance issues during simultaneous photo uploads, an SQS queue should be introduced between S3 and Lambda to buffer events and allow controlled processing, and the DynamoDB tables' Write Capacity Units (WCUs) should be evaluated and adjusted to handle the write load.
RCUs (Read Capacity Units) address read performance, but the problem explicitly identifies DynamoDB issues when data is 'saved', indicating a write capacity problem.
The problem states performance issues when data is 'saved' to DynamoDB, which directly relates to write capacity, making the evaluation and adjustment of Write Capacity Units (WCUs) crucial for performance and reliability.
ElastiCache is a caching service primarily for reads and would not address Lambda concurrency limits or DynamoDB write performance issues.
Adding an SQS queue between S3 and Lambda decouples the services, buffering events and preventing Lambda concurrency limits from being hit during high simultaneous uploads, which significantly improves reliability and allows for reprocessing logic.
S3 Transfer Acceleration speeds up data uploads to S3, but it does not resolve Lambda concurrency limits or DynamoDB write performance problems once data is in S3.
Concept tested: Lambda Concurrency, DynamoDB Capacity Units, SQS Decoupling
Source: https://docs.aws.amazon.com/lambda/latest/dg/invocation-asynchronous.html
Community Discussion
No community discussion yet for this question.