Alec Lieberman developed a robust TTL state model for Cosmos DB within the Azure/azure-sdk-for-rust repository, focusing on backend development using Rust. He introduced a TTLState enumeration to replace the previous duration-based approach, enabling explicit handling of expiration states and aligning closely with Cosmos DB TTL semantics. Alec refactored deserialization logic to map TTL values directly to the new enum, which eliminated edge-case panics and clarified behavior across different configurations. This work improved safety, reduced runtime errors, and enhanced developer ergonomics for TTL-related code paths, demonstrating a thoughtful approach to reliability and maintainability in Rust-based backend systems.