To centrally store configuration settings and application passwords in the most cost-effective way, which AWS service should you use?

AWS Systems Manager Parameter Store is the most cost-effective solution for centrally storing configuration settings and application passwords because it offers a free tier that covers most common use cases, including standard parameters. It's designed for secure storage and retrieval of configuration data. AWS Secrets Manager is also suitable for storing secrets, but it is a paid service primarily designed for automatic rotation, auditing, and fine-grained access control of database credentials, API keys, and other secrets, making it more expensive if these advanced features are not required. AWS Config monitors and records AWS resource configurations and changes, not for storing application settings. Amazon S3 is object storage and while it can store files containing configuration data, it lacks the built-in security and parameter management features of Parameter Store or Secrets Manager.