First, determine your tolerance. How much does downtime per min cost you? How long can you be down? A lot of the time it may be cheaper to apologize to your customers than build a truly reliable system.
Then start looking at points of failure and sort them based on severity and probability. Is your own software deployment going to generate more downtime per year than a regional aws outage?
There are formal academic ways to determine what your overall availability is, but don't have those on hand. Suffice to say, it takes significant research, planning, execution, and testing to ensure a target availability. (See Netflix https://medium.com/netflix-techblog/the-netflix-simian-army-... ) if someone says they have 99.9% or better up time, they had better have proof in my mind (or a fat SLA violation payout)
People outsource to cloud providers not because they are cheap, but because managing infra in house is hard. Also move fast and break things.
Read AWS docs about availability, there are availability zones in a region, spread across those to minimize impact. Then test when something goes down. Fix/repeat.
Then start looking at points of failure and sort them based on severity and probability. Is your own software deployment going to generate more downtime per year than a regional aws outage?
There are formal academic ways to determine what your overall availability is, but don't have those on hand. Suffice to say, it takes significant research, planning, execution, and testing to ensure a target availability. (See Netflix https://medium.com/netflix-techblog/the-netflix-simian-army-... ) if someone says they have 99.9% or better up time, they had better have proof in my mind (or a fat SLA violation payout)
People outsource to cloud providers not because they are cheap, but because managing infra in house is hard. Also move fast and break things.
Read AWS docs about availability, there are availability zones in a region, spread across those to minimize impact. Then test when something goes down. Fix/repeat.