The new default majority write concern in MongoDB 5.0 provides stronger durability guarantees, ensuring that acknowledged data can survive replica set elections and complete node failures. This change is rooted in the evolution of MongoDB technology and the experience from its users' workloads, particularly with the introduction of multi-document ACID transactions, support for streaming replication and replicate-before-journing, and changes to the default connection string used by Atlas drivers. The new w:majority default setting allows for a stronger durability guarantee without imposing significant performance trade-offs, making it fully tunable so that users can maintain their previous w:1 default or custom write concerns. Users who do not set any explicit write concern will be upgraded to the new default, and developers should explicitly set their default write concern to w:1 if they want to continue using the previous behavior.