I wrote a blog series that just got picked up on the main Wikimedia blog about my work migrating Wikimedia wikis to Thumbor for media thumbnailing:
Part 1: https://blog.wikimedia.org/2017/12/09/thumbor-journey-rationale/ Part 2: https://blog.wikimedia.org/2017/12/09/thumbor-journey- thumbnailing-architecture/ Part 3: https://blog.wikimedia.org/2017/12/09/thumbor-journey- development-deployment-strategy/
There's also a set of wiki pages with all the gory technical details of the setup: https://wikitech.wikimedia.org/wiki/Thumbor