Unique index duplicate key check searches for the key's existence before insertion into the index. search_near cursor API is used for the purpose. With durable history, the search through a table with a lot of deleted content became more expensive hence causing regression with insertion into the unique indexes. A prefix-search API was added that would cause search_near to early exit if the search was past the prefix. The prefix-search is being replaced by a feature to configure bounds on a cursor.

An existing prefix search can be replaced with a cursor bound on the prefix. This ticket will do so for the above-mentioned unique index usage in the server.