Unlike the sibling comments, I would call this a rolling deployment: you are removing an old host and adding a new one at the same time when you restart. In a

Unlike the sibling comments, I would call this a rolling deployment: you are removing an old host and adding a new one at the same time when you restart. In a blue green deployment I would expect to see you add backend3 and backend4 with the updated code, and then rename services (or redirect traffic in some other way) to them. The difference is, if something goes wrong, backend1 and backend2 are hot standbys and we can revert the change by redirecting traffic back to them.