Today the server can recover from index builds during a rollback getting cancelled with the use of resumable index builds. This comes at a cost of having to relax some of the invariants that rely on durable and in-memory states staying in sync during the constraints checking phase.

One of these places is the IndexBuildInterceptor, which does have a flag to indicate whether this is a resumed index build or not.

However, the DuplicateKeyTracker does not have such a flag and so it will not skip the checks when draining the writes. This can result in hitting an invariant that enforces the in-memory count to reflect the durable count.