Remote code (for developers)
You are working remotely from Russia (Ural) for Los Angeles financial startup. There is a production server there, many people working on it concurrently. The main rule: there can't be any downtime for server (even if in a second thousands of users do selects, inserts and etc.). You need to modify a column type in 4M rows database there and also make changes in code that works with this column.
Problem: there is a latency between you and server, also if you modify code and DB migration is not ready — downtime occurs. If migration ready, but code is not uploaded yet — downtime occurs. You have no time to use replication or similar time-consuming activities (have only 2 hours to solve).
What would be your approach and solution for this case?