MongoDB Write Concern, Journaling, and the Durability Illusion: What w:1 Actually Guarantees

MongoDB Write Concern, Journaling, and the Durability Illusion: What w:1 Actually Guarantees Most Go services that talk to MongoDB treat w:1 as "write succeeded." That's a category error. w:1 is an acknowledgment that the primary received the write and applied it to its in-memory view. Whether that data survives a sudden primary crash before the next journal flush depends entirely on how you've combined write concern with journaling, and most production codebases get this combination wrong because the driver defaults are designed for throughput, not durability. This article is about the mechan