Let's say we have two Spark data frames, one with 100 million records and another with 1,000 records, and we need to join the two. According to you, what is the best approach to doing this?

As one DataFrame is very small, we will use Broadcast Join. In Broadcast Join, the smaller data set is sent across the network. So, while joining with larger data set partitions, the smaller data set is available in every node.