There was no reduction, it was intended as a pointer to one data structure some TSDBs are using underneath. I would bold and highlight the "etc" present there

There was no reduction, it was intended as a pointer to one data structure some TSDBs are using underneath. I would bold and highlight the "etc" present there for you if the markup allowed it. I hope a reader would become interested in what an LSM tree is (and perhaps as importantly isn't)