A data engineer needs to batch index large amounts of textual data on an article website and provide deep keyphrase searching to end users through an app. Which AWS service could help the engineer accomplish this?

The correct choice, Amazon OpenSearch Service, is ideal for the scenario described because it is specifically designed for searching, analyzing, and visualizing large volumes of data in near real-time. OpenSearch provides full-text search capabilities, which are crucial for deep keyphrase searching across textual data. The service supports complex queries that allow users to find articles based on specific phrases, keywords, and other attributes, making it a suitable option for enhancing user experience on an article website.

Furthermore, OpenSearch can efficiently handle batch indexing of large data sets, which is necessary for processing a high volume of articles. It can store and retrieve data quickly, ensuring that searches are fast and responsive.

The other services listed do not focus on the same capabilities as OpenSearch. Amazon Athena primarily serves as an interactive query service that allows users to analyze data in Amazon S3 using SQL but does not provide the search functionalities needed. Amazon Redshift is a data warehousing service designed for querying large datasets but is not optimized for full-text search and indexing like OpenSearch is. Amazon QuickSight is a business intelligence tool for data visualization and reporting but does not specialize in search functionalities for textual data.