References
Here's the list of some of the best content on the topic of SRE:
Basics
https://sre.google/sre-book/table-of-contents/ - By far the best source to get started
https://cloud.google.com/blog/products/devops-sre/four-steps-to-jumpstarting-your-sre-practice
Databases
Availability
Scalability
https://cloud.google.com/architecture/scalable-and-resilient-apps?hl=en
SRE
Non-Abstract Large System Design (NALSD) Chapter in the SRE book, the SRE Classroom site, the Coursera Course to study
Google Official Blog: SRE: Time, technology and leaping seconds
Google Research Blog: Site Reliability Engineers: Solving the Most Interesting Problems
Videos:
Why Did We Think Large Scale Distributed Systems Would be Easy? (Puppet Conference 2013)
Keys to SRE at Google - SREcon14 Keynote speaker, Ben Treynor (VP, Site Reliability Engineering)
Infrastructure & Ops: How Google Does Planet-Scale Engineering for Planet-Scale Infrastructure - Philip Beevers (SRM - London) presentation at GCPNext (October 2016)
Metrics