This assumes all the software your stack uses and you deploy is completely bug free. While rare, bugs can occure that have been in production for a long time and those will only occur when you hit a certain conditions. Now, all your services are down. 100% is impossible.
Also, if there is a problem with one component of your stack that could have run off a cloud services, chances are Google, or Amazon will fix your edge condition much quicker then you.
Also, if there is a problem with one component of your stack that could have run off a cloud services, chances are Google, or Amazon will fix your edge condition much quicker then you.