Worked on the hapifhir/hapi-fhir repository to address a concurrency issue in backend code validation workflows. Focused on the WorkerContextValidationSupportAdapter, the developer implemented a concurrency-safe approach by ensuring that code validation against ValueSets and CodeSystems mutated a copy of the result object rather than the original, thereby preventing data corruption in multi-threaded environments. This solution was reinforced with a regression test to guard against future reintroduction of the bug. The work demonstrated practical application of Java and concurrency concepts, as well as FHIR validation expertise, contributing to more reliable and robust validation processes within the codebase.