Safa Safari contributed to the breez/spark-sdk repository by implementing a BOLT11 Invoice Expiry Option, enabling users to specify custom expiration times for invoices in seconds and supporting more flexible, time-sensitive payment flows. Working primarily in Rust, Safa focused on backend and API development, ensuring the new feature integrated smoothly with existing payment logic. Additionally, Safa simplified the test suite by removing an idempotency-key-with-expiry test for Lightning payments, reducing maintenance overhead and clarifying test coverage. The work demonstrated a targeted approach to both feature development and codebase maintainability, with thoughtful attention to the evolving requirements of payment processing systems.