No, there are no indexes in QuestDB in the article. None. Zero.
That's bold mistake in the ClickHouse article. Should be named Yes, QuestDb is Faster.
If it was demonstrated that Quest did a better job overall in the majority of cases where an optimization would have been missed, that's one thing. But this feels awfully nitpicky.
While it can help to win this very benchmark it's questionable whether it's usable in practice. Chances are an analytical database serves queries of various shapes. If you only need to run a single query over and over again then you might be better off with a stream processing engine anyway.