Which AWS service can run a managed PostgreSQL database that provides online transaction processing (OLTP)?
Amazon DynamoDB
Amazon Athena
Amazon RDS
Amazon EMR
Explanations:
Amazon DynamoDB is a managed NoSQL database service, not designed for PostgreSQL or OLTP.
Amazon Athena is an interactive query service for analyzing data in S3 using SQL, not for OLTP.
Amazon RDS (Relational Database Service) supports managed PostgreSQL databases and OLTP workloads.
Amazon EMR (Elastic MapReduce) is used for big data processing, not for running a PostgreSQL database.
I evaluate that the answer is:
Amazon RDS