AWS Glue and S3 Tables Both Use Iceberg REST Catalog but Differ in Design

AWS implements the Iceberg REST Catalog specification through two separate endpoints: the Glue Iceberg REST endpoint and the Amazon S3 Tables Iceberg REST endpoint. While both conform to the same OpenAPI-based standard, Glue is architected as an entry point to multiple catalogs, whereas S3 Tables serves as an entry point to a single table bucket. This structural difference is reflected in their URL path patterns, SigV4 signing service names, and access control mechanisms — with Glue using IAM plus Lake Formation and S3 Tables relying solely on s3tables IAM actions. An AWS Community Builder explored these differences by bypassing client libraries like PyIceberg and calling the REST APIs directly. The experiment revealed that despite sharing the same specification, the two services serve distinct architectural purposes within the AWS data ecosystem.