It's a database for a metric platform.

Think of OpenTSDB and Prometheus. Or for a better comparison think of Thanos https://thanos.io/

As to whether they could fulfil Uber's needs, the thing about scale (real massive scale - I work at Cloudflare) is that everything breaks in weird ways according to your specific uses of a technology. The things listed above work for companies, until they don't. There's few things that seem to truly work at every scale, Kafka and ClickHouse come to mind for wholly different use cases than a time series database.