Schema migrations in PostgreSQL can lead to database locks and potential downtime if not handled carefully, especially when adding constraints like UNIQUE or NOT NULL that require full table scans and ACCESS EXCLUSIVE locks. To avoid such issues, developers can adopt best practices like creating indexes concurrently and validating constraints in stages. However, these practices alone may not suffice, necessitating the use of advanced tools such as Atlas and Neon. Atlas, a schema management tool, provides static analysis to catch risky migrations before they reach production, while Neon offers database branching for realistic pre-deployment simulations. By integrating Atlas into CI/CD pipelines and using Neon’s branching capabilities, teams can effectively prevent database locks and ensure smoother migrations, ultimately fostering a more confident approach to database schema changes.