90 days is a pretty standard backup policy and a good length of time to keep backups for in case you have to go back and investigate something. AWS S3 has some other tiers now that might make it cheaper than going straight to the glacier level.
For one of our MySQL databases, we take periodical full snapshots, on the filesystem level, and then incremental snapshots of the filesystem to backup it up frequently and have an easy way to get a point in time recovery. We also backup our binary logs. Setting the retention to 90 days for all of them. We’re using Wasabi right now though.
For CDN, does this software work with Cloudflare yet? I can just turn the domain on in my enterprise account which would not cost me anything extra.