I am wondering have you considered the open source NewSQL database solutions like TiDB, CockroachDB? They have the best of both traditional RDBMS and NoSQL and would be the perfect choice to the hyper-growth scenarios.
TiDB could be considered as a scale-out MySQL and CRDB a scale-out Postgres. They are all Spanner-inspired solutions that can help avoid manual sharding.
TiDB could be considered as a scale-out MySQL and CRDB a scale-out Postgres. They are all Spanner-inspired solutions that can help avoid manual sharding.