I've tested Backblaze B2 as a storage option, and I found that with the level of traffic a typical map backend incurs, there were enough 503 errors to cause problems. This is an intentional trade-off of the B2 design that allows them to set an aggressive price point: https://www.backblaze.com/blog/b2-503-500-server-error/

I'm constantly evaluating all of the different deployment combinations and new features on cloud providers, so part of the service I'm offering is advice for your specific provider and this workload.