Project Shield is an initiative to use Google’s infrastructure to protect free expression online. The service currently combines Google’s DDoS mitigation technologies and Page Speed Service (PSS), which allow websites to serve their content through Google to be better protected from DDoS attacks.
This service allows your site to be always “online” as the original site is always shielded behind the software.
https://www.youtube.com/watch?v=wmTvv8ISwPA