The async IIFE in backupDB contains two try-catch blocks that guarantee it will never reject.
As such, we're safe to ignore the unused-promise Flow lint. Our primary reason for enabling that Lint is to catch unhandled promise rejections within keyserver, but there is no potential of that here.
Regarding the void keyword: the Flow team recommends using the void keyword to silence the unused-promise Lint. See the "Fire-and-forget" part of this blog post.
Depends on D10177