Replica set with differing index ch 5.4 server shut down

in 5.4 part 3 in making a unique index for the secondary I see that the server must be shut down, then brought up stand alone - - and then after the index is made - - shut down again and brought back up again as a replica node.

just idle curiosity as to whether this process then demands the index get created during a maintenance period in the real world or whether such a task is okay to do during hours of normal operation.

You can’t create a separate index on a Secondary node without performing those procedures, so considering that this is the only way to do it, it’s safe to assume that it’s perfectly fine to run it during normal operating hours as long as you have enough electable nodes. But of course if you have a maintenance window coming up, it’s obviously better to wait until then.

With MongoDB’s Ops Manager and Cloud Manager, you should be able to perform all this more seamlessly.