Lucene doesn't have to commit document updates to make them searchable. You just need to grab the IndexReader via the IndexWriter.getReader() method instead of

Lucene doesn't have to commit document updates to make them searchable. You just need to grab the IndexReader via the IndexWriter.getReader() method instead of opening an IndexReader on the index directory. We use this for NRT indexing currently on our site and it works fine - there's a small (500 millisecond or less) delay in changes appearing but it's close enough for us. We don't use Solr, though - it's a custom search engine based on Lucene.