After Python 2 was sunset, the Zymergen team committed to upgrading its codebase to Python 3 within one work week. Although the Python Software Foundation recommended that users convert the codebase to backwards compatible Python 3 code while running Python 2 before updating the Python version to 3.6, Zymergen used a faster, less iterative approach. In the first week, one engineer conducted a risk analysis to identify challenging problems that the team might encounter. The following week, the entire team worked only on fixing failing tests identified through the continuous integration that the engineer had implemented before merging their working branch and fixing unforeseen bugs. The authors describe other high uncertainty and/or all-or-none contexts where this approach might work. They also identify the communication and planning behaviors that enabled their success.