At a previous job what I did to prevent that was to have a special DB table that would signal what capabilities the database has, and the code would read that table and compare to its own requirements. If a capability required by the database was not present in the code (e.g. code not updated for a new feature) the code would refuse to make any writes to the DB and error all incoming requests. Likewise if a capability required by the code was missing from the database (e.g. code deployed too soon and database migration not run yet) it again would refuse requests. Before setting a feature to required in the DB and preforming the migration with feature flags, we could check all known application servers were reporting compatibility with the new feature (if any were down or not reporting at the time, they will be blocked in the next step - prioritizing safety over liveness)