Google launching Spanner is generally a positive thing for our industry and our product. It's more proof that what we're aiming for is possible and that there's demand for it. We expect that in five years, all tech companies will be deploying technology like ours.
One of the big differences is that Spanner only uses SQL for read-only operations, with a custom API for writes. We use standard SQL for both reads and writes, which means we also work with major ORMs like GORM, SQLAlchemy, and Hibernate (docs should be live today or tomorrow). Spanner's custom write API will make it difficult to work with existing frameworks, or to convert an existing application to Spanner.
Cloud Spanner only works on Google Cloud and is a black-box managed service. CockroachDB is open source and can be run on-prem or in any cloud on commodity hardware. (We don't offer CockroachDB as a service yet, but may in the future)
At this point, both products are still in beta and are still missing features like back-up and restore (according to the Quizlet blog post). We plan to launch CockroachDB 1.0 with back-up / restore enabled.
* For anyone wanting to know more about how we make CockroachDB work without TrueTime, see our blog post: https://www.cockroachlabs.com/blog/living-without-atomic-clo...