Worked on the prometheus/node_exporter repository to enhance reliability in filesystem monitoring by addressing a bug affecting read-only mount detection. Focused on backend development using Go, the work involved fixing the mountOptionsString function to properly concatenate mount options, ensuring that isFilesystemReadOnly could accurately identify read-only mounts in complex scenarios such as ZFS and ext4 remounts. Added comprehensive regression tests to validate multi-option behavior and prevent future regressions, thereby improving alerting fidelity and incident response. Optimized code performance by preallocating result slices during option concatenation, demonstrating attention to both correctness and efficiency in backend testing and implementation.