In Chapter 2, Lecture 1, the example creates an index on SSN field. I think that we will need the index in that field anyway to avoid collection scan. May I ask if it’s a good option as usually SSN is unique per person? So we may end up with a very big index with different values. Is it good practice? I’m asking for my curiosity here only as I belive that we don’t have the option to not create the index on SSN field if we need to search on that field anyway.
Creating indexes with high cardinality fields (like an SSN) is good practice. It can be combined with other good practices like making that field part of a compound index and following the Equality Sort Range (ESR) recommendation for which fields to use in the compound index.
This and several other recommendations / good practices are discussed in this blog post..
Hope this helps answer your question and good luck with the rest of the course!