One challenge is latency in the generation of codebase and identifier and callgraph search index (Cf., Code Search and Kythe). We can perform global tests acro

One challenge is latency in the generation of codebase and identifier and callgraph search index (Cf., Code Search and Kythe). We can perform global tests across the entire monorepo, but that takes time. What happens if someone introduced new usage of old API immediately before our atomic refactoring, and what about pathological tests or flakes? This still necessitates doing some cleanups multi-stage: (1.) mark old API as deprecated (optionally announce), (2.) replace and delete legacy usages, and (3.) deletion of final trailing usage sometime soon thereafter once the codebase has been reindexed. Some languages and ecosystems are more tolerant of this problem than others. That said, incremental cleanup still has advantage with bisecting regressions. As I said, it is not perfect but broadbased change quickly is relatively easy. In my time maintaining open source, I never had these luxuries, which is why I said the monorepo is infinitely easier. Another consequence: if global cleanups are easy, perhaps that reduces the barrier to experimentation. Perfect is no longer the enemy of the good and the good enough. For me, I felt in open source where I had zero control over dependent code and its callgraph, the reverse was true: hesitance to publish something for fear of cost.