Type	Examples
RDBMS	MySQL, PostgreSQL, Oracle Database, Microsoft SQL Server, MariaDB
Cloud-based, relational databases	Cloud SQL, Cloud Spanner, AlloyDB
NoSQL	Key-value pair: DynamoDB Columnar: Snowflake Document: MongoDB, DynamoDB, CosmosDB Graph: ArangoDB Time series: InfluxDB, KairosDB, Prometheus, ClickHouse
Cloud-based, NoSQL databases	Cloud Firestore
In-Memory Databases	Redis, SAP HANA, Oracle TimesTen

Resources

1. Types of NoSQL databases
2. What is NoSQL?
3. What is a relational database?
4. What Is an In-Memory Database?