Everything you need to understand about persisting data to a physical medium has be written by richard hipp et al. You can't cheat. You can easily write async write calls in your own app to a synchronised storage engine and not assume the cost. When you have to have written logs which are accessed by government agencies you need to think about the atomicity of what a transaction is in you business. Is it when it enters the building as an electrical signal or when you flip the bits on a spinning disk

Methinks the world has forgotten that high throughput systems existed long before the web of recent years. Most of what the web world thinks is high throughput is hilariously slow. The ability to run up another instance to scale sideways has ruined people. It doesn't scale in a linear fashion.