There's an option in Search 5 related to non-exclusive index use: https://docs.jboss.org/hibernate/search/5.11/reference/en-US/html_single/#lucene-indexing-performance

By setting exclusive_index_use to false, Hibernate Search will commit after every workset and will release locks after every commit.

Performance will be terrible, and there's just no good reason to do this now that we provide an Elasticsearch backend capable of sharing index data across multiple nodes.

Let's remove this feature. If someone asks for it and provides a reasonable use case, we will reconsider, but we will not waste time optimizing performance for non-exclusive indexes.