SQLite has been the most used DB for quite a while, by orders of magnitude. It's in every browser, on every phone, lots of desktop apps, ....
Now there are a bunch of new companies that also want it to take over in the more traditional domains.
So far I don't see a lot of uptake. It's still vastly inferior to the more entrenched databases. Both in terms of performance - especially under concurrency, and in available featureset.