Without getting into a lot of details and disclosing IP, can people talk about systems they use for search backend/retrieval? Some of the things I know companies use are, Solr/ElasticSearch/Lucene and other custom in house systems etc. I am thinking of search applications on web or apps like google web search, or bing search or linkedIn job search or airbnb rental search etc.
in house, obviously. save yourself the headache and ignore elastic search. it is not elastic.
The thread title reads like you're looking for colonoscopy equipment lolol!!
In-house, though the open source ones are good enough for any application we might build in our spare time. What exactly are you looking for? There are certain tradeoffs to be aware of when building web scale capabilities.