If you took my advice from the other day and had a look at MongoDB’s excellent Web Shell then you’ve probably tried out a few commands, maybe even worked through a bit of the tutorial. But you’re not only a busy developer, you’re an experienced developer. You know your way around and you don’t want to waste time with superfluous details. You want answers and you want them now. You can handle the truth. In short, what you want is a quick reference guide.

When it comes to quick reference guides I have 2 requirements (apart from the content being half decent):

1. They must be printable on regular sized (A4) paper.
   This makes PDF my preferred format.
   As a bonus, this also makes them easy to store, search and annotate in Evernote.
2. They must be readable.
   I’m too old to be squinting at an illegible, 8 point font.

So, bearing those criteria in mind, here are the best of the free MongoDB quick reference guides:

• MongoDB Shell Cheat Sheet (http://www.hodgin.ca)
  A comprehensive one-sheet covering Database Administration, CRUD Queries, Analytic Queries, and System Administration.
  The text is fairly dense and would be improved by spreading it over two pages but this is still one of the best MongoDB reference cards.
• MongoDB Quick Reference Cards (mongodb.com)
  These are the official reference cards from MongoDB, Inc. There are four 2-page guides available covering ‘Queries and Updates‘, ‘Indexing‘, ‘Replication‘ and ‘Mapping SQL to MongoDB‘. A further two cover the C#/.Net driver.
  These are my favourite reference cards – frequently updated and cleanly and clearly laid out. They may be downloaded individually or as a set.
• MongoDB Cheat Sheet (codecentric.de)
• MongoDB Cheat Sheet (cheatography.com)
  Covers only the most basic commands. Abandoned?
• MongoDB Cheat Sheet (krablekod.ru)
• The Little MongoDB Book by Karl Seguin (openmymind.net)
  Not a quick reference guide but a 30-page booklet. Apart from the intro and outro this is mainly a handy reference guide so a useful one to have on your desk.
• MongoDB Cheat Sheet for Java Developers (saville.cloudcontrolled.com)
  Like “The Little MongoDB Book” this is too long for a cheat sheet (it’s 10 pages) but it’s intended for use by those studying the M101J course taught by MongoDB, Inc and is conveniently arranged with a section for each class.
• Migrating from SQL to MapReduce with MongoDB (rickosborne.org)
  Described as a “Nice infographic of how the clauses in a moderately-complex SQL statement relate/translate to the JavaScript of MapReduce functionality in MongoDB”. Which is exactly what it is.
• MongoDB: Flexible NoSQL for Humongous Data (refcardz.dzone.com)
  Written by Christina Chodorow, so you know the content is good, but requires a (free) account to download.