Worked on the aws/amazon-s3-encryption-client-java repository to enhance the reliability of S3 instruction file uploads by ensuring accurate content-length handling in PutObjectRequest operations. Addressed edge-case failures by updating the InstructionFileConfig to derive content length from the actual byte length of instruction file content, which improved the robustness of backend processes. Developed and integrated comprehensive unit tests for both synchronous and asynchronous S3 clients using Java, verifying correct behavior and preventing regressions. Focused on backend development and AWS S3 integration, the work contributed to a more reliable customer experience by reducing upload errors and strengthening the overall upload workflow.