Amazon DynamoDB and DataStax Cassandra are similar on masterless architecture and principles, DynamoDB is managed and needs cost analysis. If you need to have better control, DataStax is better.I also did a prototype with Google Spanner in one of the recent innovation days, it provides the best of both worlds but being a service on Google Cloud Platform(GCP) works if your services are primarily on GCP. Amazon Aurora is a relational database with higher performance and is a good candidate if search and default relational behavior is preferred.For now, DataStax worked well for us as it provides best in class performance across different kinds of read/write/mixed workloads. It provides linear scalability which works for the best performance, lowest latency and highest throughput. If configured correctly, there is no downtime and no data loss.