Worked on the MHSanaei/3x-ui repository to address a critical routing issue by fixing a bug in geosite handling. The solution involved normalizing country codes to uppercase during geofile updates, which eliminated case-sensitivity lookup failures in the Xray-core router and improved compatibility with various geosite providers. This backend improvement, implemented in Go, directly enhanced system stability and reduced support overhead by ensuring consistent routing behavior for end users. The work demonstrated a strong focus on backend development and API reliability, with careful documentation and integration of the fix to support ongoing maintainability and interoperability within the project’s infrastructure.