There is lot of statistical and empirical data on this topic - MTBF estimates from vendors (typically 100k - 1m+ hours), Backblaze and Google drive failure data (~1-2% annual failure rate), IEEE and others. With N+1 redundancy (backup servers/RAID + spare drives) and proper design and change control processes, operational failures should be very rare.

With cloud hardware issues are just the start - yes you MUST "plan for failure", leveraging load balancers, auto scaling, cloudwatch, and dozens of other proprietary dials and knobs. However, you must also consider control plane, quotas, capacity, IAM, spend, and other non-hardware breaking points.

You're autoscaling isn't working - is the AZ out of capacity, did you hit a quota limit, run out of IPv4s, or was an AMI inadvertently removed? Your instance is unable to write to S3 - is the metadata service being flakey (for your IAM role), or is it due to an IAM role / S3 policy change? Your Lambda function is failing - did it hit a timeout, or exhaust the (512MB) temp storage? Need help diagnosing an issue - what is your paid support tier - submit a ticket and we'll get back to you sometime in the 24 hours.