It is significantly more likely that the internet between you and your closest S3 nodes is blocked than S3 is down. AWS has experienced severe outages in the past, as in 2017, but even these are usually only for a few hours, and more local problems are more common but even more quickly fixed… in fact, because AWS can shift the load to nearby nodes while they fix the problem, these troubles mostly manifest as a temporary slowdown, rather than an outage per se. AWS has an average of ~1.2 incidents per year they consider worthy of making specific after-action reports on, consisting of actual disruptions, and even these generally are contained to specific regions.