Problem

In disaggregated storage, a collection and its index can become inconsistent with each other: the two tables do not reflect the same state, so index entries and collection records disagree.

Observed in the disagg_concurrency_replication suite as:

• validate failure: "number of _id index entries (0) does not match the number of documents in the index (1000)" (agg_sort)
• DataCorruptionDetected: "Erroneous index key found with reference to non-existent record id" (create_index_background_unique)