MongoDB has dropped ACID compliance and is introducing multi-document transactions in its 4.0 version, enabling developers to model their data in a more flexible way while still maintaining transactional integrity. Transactions will be available across a single replica set in MongoDB 4.0 and across a sharded deployment in MongoDB 4.2. The technology has been developed over three years and provides fine-grained consistency and durability guarantees, as well as a global logical clock. Transactions will feel familiar to developers with prior transaction experience and will provide critical peace of mind for many applications.