The text explores the differences in how Postgres and MySQL handle foreign key definitions, highlighting a critical syntax distinction that can lead to unexpected behavior during database migrations. In Postgres, foreign key constraints are enforced even when defined inline with the column definition, ensuring referential integrity and preventing data inconsistencies. Conversely, MySQL does not enforce inline foreign key constraints, treating them as comments unless explicitly defined using the FOREIGN KEY keyword, leading to potential data integrity issues. The article advises developers to review schema definitions when migrating from MySQL to Postgres, emphasizing the importance of explicitly naming foreign key constraints to ensure consistent behavior across different database systems. It concludes by encouraging rigorous testing and suggests Neon as a developer-friendly Postgres solution for those interested in exploring database branching.