The shadow replicas feature (added in #8976) has not seen the amount of usage we originally hoped for. On the flip side it is very tricky to maintain, effectively adding a second replication logic. Example issues include #22021 , #17695, #16358 , #13583 , #16357 - see here for more. It is also requires new features (like sequence numbers) to be implemented for both normal replicas and shadow replicas, increasing the amount of future work.

Given the lack of uptake we are considering to remove them (and will mark them as deprecated in a separate PR).

This is issue is opened as a placeholder for discussion and to give people the option to object and state their use case.