X, a social media app with nearly 500 million users worldwide, has recently updated its Android app's login process by implementing passkey authentication. This new feature aims to provide a safer, more seamless sign-in experience for users, eliminating the need for passwords and enhancing account security. Passkeys rely on public-key cryptography, making them unique and tied to the website or app, and cannot be phished. X developers used Android's Credential Manager API to integrate passkeys, which simplified the process and reduced code, bugs, and maintenance overhead. The migration took only two weeks to complete, followed by an additional two weeks to fully support passkeys. By adopting passkeys, X developers achieved an 80% code reduction in the authentication module, a 90% resolution of legacy edge case bugs, and an 85% decrease in GIS, One Tap, and Smart Lock handling code. The team also saw a substantial reduction in login times and a doubling of the app's successful login rate compared to when it only relied on passwords. X plans to further enhance the user experience by allowing sign-ups with passkeys alone and providing a dedicated passkey management screen.