AWS Certified Solutions Architect – Professional — Question 303

A company hosts a blog post application on AWS using Amazon API Gateway, Amazon DynamoDB, and AWS Lambda. The application currently does not use
API keys to authorize requests. The API model is as follows:
GET/posts/[postid] to get post details
GET/users[userid] to get user details
GET/comments/[commentid] to get comments details
The company has noticed users are actively discussing topics in the comments section, and the company wants to increase user engagement by marking the comments appears in real time.
Which design should be used to reduce comment latency and improve user experience?

Answer options

• A. Use edge-optimized API with Amazon CloudFront to cache API responses.
• B. Modify the blog application code to request GET comment[commented] every 10 seconds.
• C. Use AWS AppSync and leverage WebSockets to deliver comments.
• D. Change the concurrency limit of the Lambda functions to lower the API response time.

Correct answer: C

Explanation

AWS AppSync natively supports WebSockets, which enables real-time, two-way communication to push comments to active clients instantly. Regular polling (Option B) introduces unnecessary overhead and delay, while caching (Option A) would prevent users from seeing live updates. Adjusting Lambda concurrency (Option D) manages scaling but does not establish a real-time push mechanism for the client.