Which analytical service allows users to perform complex queries on large datasets stored in S3?

Amazon Athena enables users to perform complex queries on large datasets stored in Amazon S3 using standard SQL. This service is particularly powerful because it is serverless, which means there is no need to manage any infrastructure. Users can simply point Athena at their data in S3, define the schema, and run SQL queries directly on the data. This allows for real-time analytics without the need to move data into a separate analytics platform.

Additionally, Athena supports various data formats such as CSV, JSON, ORC, Avro, and Parquet, making it versatile for different types of data storage. The pay-per-query pricing model allows users to only pay for the queries they run, providing cost efficiency for organizations that need to analyze data intermittently.

In contrast, AWS Glue is primarily an ETL (Extract, Transform, Load) service that prepares and transforms data for analysis rather than executing complex queries directly. Amazon Redshift is a data warehousing solution that allows for extensive analytics but requires data to be loaded into the warehouse rather than querying data stored in S3 directly. AWS EMR (Elastic MapReduce) allows for processing vast amounts of data using frameworks like Apache Spark and Hadoop but involves more setup and management compared to the simplicity of using Athena.