[p4lindromica]

I think this article misunderstands the implications of the fire and forget write concern. Fire and forget means that mongo has acknowledged a write that may not be persisted to disk. It appears the author uses fire and forget for notes, which are acceptable to lose, and tracking information, which are not acceptable to lose.

The author states the only downside of fire and forget is that data may not be available on subsequent queries. While this may be true, this should not be what you are worrying about. The downside is that when your primary crashes, or becomes overloaded to the point where your slaves all are lagging significantly and you need to switch primaries, the data is inconsistent and you will lose that acknowledged write.