Specifying true directs MongoDB to build the index in the background. Background builds do not block operations on the collection. Since MongoDB 4.2 indices are built on the background by default. In MongoDB 4.0 and before, this defaults to false.
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Specifying true directs MongoDB to build the index in the background. Background builds do not block operations on the collection. Since MongoDB 4.2 indices are built on the background by default. In MongoDB 4.0 and before, this defaults to false.