Based on our investigation, we found that most Apple Developer Academy members use locker to store their things, but they face some difficulties, such as having trouble when looking for empty lockers and forgetting their locker position/locker password. It’s difficult to find and empty lockers because they stated that there’s no indicator and when they realized that the indicator come in form of lamp, they don’t notice it. Some Apple Developer Academy members forget their locker position because they didn’t use their usual locker due to being occupied by others. To counter this problem we summarize criteria for the solution, which reduce time taken when searching for usable locker, locker’s condition must be kept according to the management rules, solution must be easy to use for users, solution can only be used within Apple Developer Academy environment, making user users cannot book the usable lockers and the media for solution is recommended as an app form. Therefore, LiLo, or Lock In Lock Out, is a locker booking system designed to streamline the process of finding and reserving lockers at the Apple Developer Academy. It provides real-time updates on locker availability and securely stores locker details, making it easy for users to locate and remember their assigned lockers. The app ensures a user-friendly experience while maintaining fair access to lockers within the academy environment.