Now in general availability, server version 4.0 support in Azure Cosmos DB API for MongoDB adds a number of new features, including multi-document transactions which make it easier to model complex transactional business logic without the complex error handling logic. The Azure Cosmos DB API for MongoDB 4.0 can be enabled on any new or existing database account in seconds, with zero downtime. Upgrading to version 4.0 can be done in the Azure Portal or through the Azure CLI.
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