Your company has built a Therapist Finder service. Since the launch last year, over 150K therapists have registered from around the country, and the service is growing rapidly. The management has decided to add a new, much-needed feature to showcase Verified Therapists based on a complex search context and other parameters on their website. Thus, when users search for related therapists, the service can show verified therapists. Their current database is in DynamoDB. The management is ready to do some reengineering if the solution can be cost-effective as well. 

Answer options:

A.Stream the DynamoDB data to Amazon OpenSearch using AWS Lambda and use it for the search.
B.Migrate the DynamoDB data to the AWS RDS database and use it for the search.
C.Use the AWS ElastiCache in front of the DynamoDB for the search queries
D.Use the DynamoDB Accelerator for faster response times and save the read capacity.

Correct Answer: A
Option A is CORRECT because moving the data to Amazon OpenSearch will give better search options without breaking the Read Capacity of the DynamoDB. Use the OpenSearch queries to boost the search result efficiently.
Option B is INCORRECT because moving the data to RDS will not solve the issue and will need significant engineering effort as well.
Option C is INCORRECT because ElastiCache is to cache the data and not run the complex search queries.
Option D is INCORRECT because DAX is not a service to help to search content and does not help to implement the feature. 
DAX and ElastiCache are used for different purposes than Amazon OpenSearch services.
DAX is better than ElastiCache but cannot be compared to Amazon OpenSearch Service.
Reference:
https://aws.amazon.com/blogs/compute/indexing-amazon-dynamodb-content-with-amazon-elasticsearch-service-using-aws-lambda/