Submission + - MySQL analysis with AnalyzeMySQL (xenji.com)
trivago's database consists of about 230 tables, many of them having a history of more than four years, some of them up to 7 years. A few of them do have some historic flaws, like having a signed bigint as primary key (because nobody could imagine what space will be needed in a few years), others do have indexes that are not longer used, etc. There are many tasks to do until you get to know the database scheme very well.
I wrote a tool to support me on my tasks. Read on, if you are interested in getting more information about it.