You've got a point. BigTable is an example; they've never open-sourced it and instead other OSS projects (notably the Hadoop ones) were inspired by it. Other e

You've got a point. BigTable is an example; they've never open-sourced it and instead other OSS projects (notably the Hadoop ones) were inspired by it. Other examples are GFS, Colossus, Spanner and F1. The OSS analogue of GFS is HDFS (AFAIK), but I know of nothing equivalent to the others. (CockroachDB is a bit like Spanner, but is much more pragmatic about its clocks.)