Glacierbase is a framework developed by WHOOP to manage schema migrations in open table formats like Iceberg. With WHOOP's data platform handling hundreds of terabytes to petabytes of data, maintaining schema consistency is critical. Even minor inconsistencies can disrupt analytics and model training. Glacierbase addresses this issue by introducing version control for schema changes, allowing teams to track updates, understand their purpose, and ensure that all environments are synchronized. The framework treats schema changes as immutable migrations, recording each change in a .sql file that includes metadata about the author and the reason for the change. This self-documenting approach makes it easier to review and understand migrations. Glacierbase supports various open table formats, not just Iceberg, by allowing configurable backend runtimes and dependencies. It provides both a Python API and a command-line interface for executing migrations, ensuring consistency across different environments. The system also locks migrations to prevent concurrent updates, which adds a layer of safety during schema evolution. Glacierbase integrates into WHOOP's engineering workflow by linking schema changes directly to code updates. When a new feature requires a schema modification, engineers create a migration file alongside the code. This ensures that changes are peer-reviewed and tested before deployment, maintaining the same rigor applied to application code. Future plans for Glacierbase include automating the migration lifecycle through CI/CD integration and transitioning to a REST-based Iceberg catalog for enhanced access control across the data lake.