But I don't want to be just snarky. We faced the very same dilemma and solved it in a similar way - we use Apache Spark, which can connect to MongoDB directly.

But I don't want to be just snarky. We faced the very same dilemma and solved it in a similar way - we use Apache Spark, which can connect to MongoDB directly. It loads fairly quickly and we can save it to Parquet on S3 directly, the whole thing is about 5 lines of code. If you have a Spark platform in place, it's a decent solution for this.