As you've mentioned, a seamless and delightful user onboarding experience is crucial to the success of your web and mobile application. My solid background in full-stack web development, particularly JavaScript and React.js, would be invaluable in creating the dual-platform username generation feature you desire. Besides ensuring cross-platform compatibility, my proficiency with integrating backend APIs will guarantee efficient username checks, eliminating any usernames that are already taken and offering similar alternatives when necessary.
Continuing with that theme of user-friendliness, I am experienced in working with user interface design and usability principles, as well as adhering to policies for character usage. That means I can implement the minimum character length validation required for registration along with providing users the option to customize their username creatively yet within the bounds of your platform's username policy.
Furthermore, my knowledge of AWS will aid in deploying and scaling up this feature effectively. My ability to architect robust and scalable applications means once built, your username generation feature will be prepared for growth as more users sign up. My commitment to staying updated on industry trends ensures you'll receive a solution that's both cutting-edge and sustainable. Let me help bring not just technicality but also creativity into this project!