Worked on the juspay/decision-engine repository to enhance mandate and e-mandate processing within the gateway decision engine, enabling accurate identification and handling of one-time mandate flows and expanding transaction coverage for improved gateway selection. Addressed robustness in gateway filtering logic by resolving syntax errors, refining authentication type validation, and adjusting cloning behavior to ensure precise routing for card mandates. Leveraged Rust for backend and API development, with a focus on payment gateway integration and data-flow reasoning. These contributions reduced edge-case failures, improved compliance, and enabled smoother mandate processing, demonstrating a methodical approach to both feature delivery and critical bug resolution.