Scalability
Look for systems that offer seamless horizontal scalability, often referred to as "sharding." A robust distributed database should allow you to add more nodes to a cluster to increase throughput or storage capacity without requiring downtime or major re-architecting of your application.
High Availability and Fault Tolerance
The database must support replication. By maintaining copies of data across different physical locations, the system ensures that your application remains accessible even during hardware failures, network outages, or entire regional cloud disruptions. Evaluate the system's "Mean Time to Recovery" (MTTR) and automatic failover capabilities.
Consistency Models
Understand the trade-offs between consistency and availability, often guided by the CAP theorem (Consistency, Availability, and Partition Tolerance). Some distributed databases, like CockroachDB or Google Cloud Spanner, prioritize strong consistency, which is vital for financial applications. Others, like Apache Cassandra, may prioritize "eventual consistency" to achieve higher write availability and lower latency.
Data Model Flexibility
Assess whether your workload requires a relational model (SQL), a document-oriented model (NoSQL), a key-value store, or a wide-column store. Modern distributed databases are often multi-model, allowing teams to store and query complex data types without rigid schema constraints.