MongoDB Atlas offers a serverless database with features such as connection over HTTP, multi-region availability, schema design limitations, and no cold starts. DynamoDB is another option for serverless databases, offering key-value and document data structures, auto-scaling, and a pay-as-you-go model. CockroachDB provides a distributed SQL database system with support for connection over HTTP, multi-region availability, dynamic schema, and ACID transactions. Fauna combines the flexibility of NoSQL with the relational querying capabilities and consistency of SQL, supporting connection over HTTP, multi-region availability, document-relational schema design, and strongly consistent distributed ACID transactions.