HaaLeo focused on backend development for the aws/aws-sam-cli repository, addressing a critical issue with API Gateway event timestamp precision. By leveraging Python’s time_ns() function and converting nanoseconds to milliseconds, HaaLeo delivered a fix that improved the accuracy of requestTimeEpoch values. This enhancement ensured that downstream analytics and billing systems received more reliable and granular timing data, directly impacting observability and data integrity. Although the work centered on a single bug fix rather than new features, the solution demonstrated a strong grasp of API development and backend engineering, with careful attention to the technical requirements of distributed event processing systems.