Hi Ere Many thanks for your thoughts and technical tips! For the moment the library decided not to load their 6 million records into Koha (with Zebra) but to index them separately, either in Vufind or in ALBERT (a discovery system developed by the KOBV, a German union catalog) which like Elasticsearch all are using Solr Lucene. The main reason for the decision is the actual development status Koha using Elasticsearch. However, this will probably be reconsiderated one day in the future when Elasticsearch is fully integrated into Koha, all/most bugs omitted, and when Zebra definitely will be gone. Best wishes: Michael -- Geschäftsführer · Diplombibliothekar BBS, Informatiker eidg. Fachausweis Admin Kuhn GmbH · Pappelstrasse 20 · 4123 Allschwil · Schweiz T 0041 (0)61 261 55 61 · E mik@adminkuhn.ch · W www.adminkuhn.ch