https://www.clever-cloud.com/blog/engineering/2015/05/20/Why-Auto-Increm...
https://devcenter.heroku.com/articles/postgresql-indexes
Here you can find links to various PostgreSQL related presentations
https://wiki.postgresql.org/wiki/PostgreSQL_Related_Slides_and_Presentations
http://tech.zalando.com/getting-a-quick-view-of-your-postgresql-stats/