A company is developing software that uses a PostgreSQL database schema. The company needs to configure multiple development environments and databases for the company's developers. On average, each development environment is used for half of the 8-hour workday. Which solution will meet these requirements MOST cost-effectively?

The most cost-effective solution is to configure each development environment with its own Amazon Aurora On-Demand PostgreSQL-Compatible database. Aurora Serverless v2 (On-Demand) automatically scales capacity up or down based on demand, and you only pay for the capacity consumed. Since development environments are used for only half of the workday, this serverless option will significantly reduce costs by scaling down to zero capacity when not in use. Configuring each environment with its own Amazon Aurora PostgreSQL database (provisioned) would incur higher costs because you pay for provisioned capacity whether it's used or not. Similarly, Amazon RDS for PostgreSQL Single-AZ DB instances are provisioned, leading to unnecessary costs during idle periods. Using Amazon S3 with S3 Object Select is irrelevant as it's an object storage service, not a relational database, and cannot host a PostgreSQL schema.