Amazon S3 Glacier is a storage service optimized for infrequently accessed data, or 'cold data', where retrieval times of several hours are suitable. It is designed for long-term storage of data that is infrequently accessed and provides high durability at a lower cost than storage options engineered for frequent access. This aligns with the company's needs to store static content that is accessed irregularly yet must be kept indefinitely. Amazon EBS and Amazon EFS are not as cost-effective as Amazon S3 for infrequently accessed and fully managed object storage. Although Amazon RDS supports BLOB storage, it is primarily used for structured data within a database and is not a cost-effective solution for the use case described.