In case of content-topic change for communities, the rollout strategy can be little different.
| Step | App Version | Read | Write |
|---|---|---|---|
| Initial | N | Old protocol | Old protocol |
| Preparation | N+1 | Old and new protocol | New protocol |
| Switch+Clean-up | N+2 | New protocol | New protocol |
We can combine and make it a 2-step migration by write/read on new protocol in N+1 and switch+cleanup in N+2. Note that this is possible because we are planning to reuse an existing content-topic as part of new protocol which makes it easier for the switch.
Also note that maybe for many cases this 2 steps approach may also be enough and can be included as an option for app devs to consider. It makes switch faster than 3 step approach and especially in scenarios where impact is higher we can suggest this 2 step approach.
yes,i was surprised at this as well, but looking at the code it does seem to be this way.