Developed a deterministic session sampling architecture for the DataDog/dd-sdk-ios repository, focusing on cross-SDK consistency for RUM, Trace, and Session Replay modules. Leveraged Swift and advanced sampling algorithms, notably implementing Knuth’s hash function to unify sampling rates and ensure reproducible decisions from UUID generation through to sampling outcomes. Enhanced the codebase with comprehensive unit tests, migrated legacy tests to a new DeterministicSampler API, and improved SwiftLint compliance for maintainability. Documented technical decisions around seed handling and float precision, supporting reliable releases and streamlined debugging. The work emphasized robust test coverage and clear documentation to facilitate ongoing development and integration.