Vanja Vujovic contributed to the apache/spark repository by developing two backend features focused on SQL performance and observability. In July 2025, Vanja introduced a SQLMetric-based instrumentation to measure remote schema fetch durations in Spark SQL, improving the ability to debug and tune distributed schema retrieval. The following month, Vanja optimized SQL command execution by reducing JDBC connection overhead, which is expected to lower latency and improve throughput for large-scale deployments. Both features were implemented using Scala and SQL, demonstrating a strong grasp of backend development and database management. The work addressed core performance bottlenecks and enhanced operational efficiency in Spark.