"It Comes in Notebooks": Changes and Challenges when Operationalizing ML Prototypes

Abstract

Machine learning practitioners commonly prototype models in computational notebooks before transitioning them to automated production systems. Despite its prevalence, the concrete engineering work involved in this transition and the software quality concerns that motivate it remain insufficiently characterized. We report on a qualitative study based on semi-structured interviews with 13 ML practitioners from industry and academia. Using reflexive thematic analysis, we identify 23 engineering changes organized into five themes: code restructuring, data pipeline development, testing & validation, pipeline automation, and monitoring & observability. We also identify 20 software quality attributes across the ML development lifecycle and map them to the engineering changes. A recurring pattern in our findings is that computational notebooks externalize oversight to the human practitioner, and defer costs that become obligatory at operationalization time. Operationalization constitutes the repayment of this technical debt accumulated during prototyping, which we refer to as oversight debt. Practitioners do not merely restructure notebook code, but repay this debt by constructing automated substitutes for the interactive oversight that notebooks provide. We further present seven quality trade-offs showing that these tensions are properties of the notebook-to-production transition, rather than symptoms of poor engineering practice. Our findings structure operationalization effort, establish empirical links between engineering changes and software quality concerns, and provide implications for practitioners, tool designers, and researchers working on ML-enabled software systems.