Worked on the Anastasia-Labs/midgard repository to enhance transaction error handling in the backend API. Focused on standardizing how missing transactions are reported, a NotFoundError class was introduced and refactored to extend Data.TaggedError, ensuring consistent error semantics across endpoints. The API was updated to return 404 for absent transactions and 400 for invalid transaction hashes, clarifying error responses for clients. Improvements to transaction retrieval logic and unified error paths were implemented to support better diagnostics and maintain backward compatibility. The work leveraged TypeScript and backend development skills, with an emphasis on robust error handling and clear client communication.