I recently deployed Quickwit (based on Tantivy, from the same team) in production to index a few billion objects and have been very pleased with it. Indexing rates are fantastic. Query latency is competitive.

Perhaps most importantly, separation of compute and storage has proven invaluable. Being able to spin up a new search service over a few billion objects in object storage (complete with complex aggregations) without having to pay for long-running beefy servers has enabled some new use cases that otherwise would have been quite expensive. If/when the use case justifies beefy servers, Quickwit also provides an option to improve performance by caching data on each server.

Huge bonus: the team is very responsive and helpful on Discord.