Form Building and Validation Questions

Design and implement robust, accessible, and maintainable user input forms. Topics include controlled and uncontrolled component patterns, accessible labeling and keyboard support, client side and server side validation strategies, asynchronous validation and debouncing, optimistic updates and rollback, error messaging and localization, security and input sanitization, multi step and large form performance considerations, and testing approaches for unit and integration coverage. Candidates should discuss trade offs between libraries and custom solutions and how to compose reusable form primitives across an application.