Summarize in 500 words or more about Spark and MongoDB from the video links below:
1.https://www.youtube.com/watch?v=QaoJNXW6SQo
2.https://www.youtube.com/watch?v=zC9cnh8rJd0
3.https://www.youtube.com/watch?v=-56x56UppqQ
4.https://www.youtube.com/watch?v=MPPwn1XmhzQ