Hitting the Iceberg REST Catalog Directly: Understanding the Differences Between Glue Data Catalog and S3 Tables

Original Japanese article : Iceberg REST Catalogを直接叩いて、Glue Data CatalogとS3 Tablesの違いを理解する Introduction I'm Aki, an AWS Community Builder ( @jitepengin ). Most of the time, when working with Iceberg tables, we reach for PyIceberg or Spark. I'm no exception, and honestly there were parts of the PyIceberg configuration — rest.sigv4-enabled , rest.signing-name , warehouse — that I understood only vaguely. Iceberg defines a standard called the Iceberg REST Catalog Open API specification , and AWS implements it through two separate endpoints: The AWS Glue Iceberg REST endpoint ( https://glue.<region>.amazonaws.com/iceberg ) The Amazon S3 Tables Iceberg REST endpoint ( https://s3tables.<region>.amazonaws.com/iceberg ) If two implementations follow the same spec, sending the same requests to both and comparing the results should reveal what's actually different between them. In this article, I'll bypass clients like PyIceberg entirely and hit the REST API directly to explore the differences between the two endpoints. To state the conclusion up front: Even though both implement the same Iceberg REST Catalog specification, Glue is designed as an "entry point to multiple catalogs," while S3 Tables is designed as an "entry point to a single table bucket." That difference is visible just by looking at the URL paths. I previously wrote about the relationship between S3 Tables and Glue Data Catalog in another article — worth a read alongside this one: Does Amazon S3 Tables Replace AWS Glue Data Catalog? Understanding Their Relationship What Is the Iceberg REST Catalog? The Iceberg REST Catalog is a specification that standardizes Iceberg catalog operations as an HTTP API. It's published as an OpenAPI definition (YAML), and any catalog that conforms to it can be accessed the same way from clients such as PyIceberg, Spark, and Trino. The key points of the spec are: URL paths follow a pattern like GET /v1/{prefix}/namespaces , where {prefix} is a free-form segment Clients first call