Pulumi provides an efficient way to manage configuration settings across multiple environments and applications by integrating with AWS Systems Manager Parameter Store. This approach is particularly beneficial for larger teams or organizations that need to maintain consistency in configuration settings across various apps. By using Pulumi's stack references alongside Parameter Store, developers can store, encrypt, and manage API keys and database credentials centrally, allowing downstream applications to inherit these settings automatically. The process involves setting up a shared configuration stack in Pulumi, which defines and stores parameters in AWS Systems Manager, and then creating additional stacks that reference and utilize these parameters, facilitating both deploy-time and runtime configuration access. This method not only ensures secure handling of secrets but also allows for flexible and immediate updates to configuration settings without requiring redeployment of downstream applications. The blog post also highlights alternative solutions such as AWS Secrets Manager for scenarios needing additional features like secret rotation and auditing.