So, after stumbling over some serious limitations with Cloud Spanner (no ORM for python, no update-by-query, index can not join to it's data table to fetch additional values) we are looking into another solution. CockroachDB looks like a good fit, except for a known limitation.
The FAQ states under "New limitations":
A limitation in v1.1 prevents meta2 from being split; thus, the max size of a single range, 64MiB by default, limits the overall size of a cluster to 64TB. Clusters beyond this size will experience problems.
- do replicas count toward the cluster size?
- will this limitation be removed in 1.2?
- if this limitation will persist for a longer while: what kind of problems will a bigger cluster face?