Quickwit
Sub-second search & analytics engine on cloud storage
... the index data structures and made search stateless and sub-second on cloud storage. Quickwit is open-source under the GNU Affero General Public License Version 3 - AGPLv3. Fundamentally, this means you are free to use Quickwit for your project if you don't modify Quickwit. However, if you do and you are distributing your modified version to the public, you have to make the modifications public.