How to speed up by avoiding flushCallbacks()

[RichardKaufmannOG]

Hi,
in my application I have an async function call to a backend api to load around 12000 data entries.
This happens in around 500ms. All this is encapsulated in an async await call.
After or during the async function returns the application hangs for around 7 seconds. With the help of profiling I discovered that the call to flushCallbacks() consumes 6 seconds. For what purpose is flushCallbacks() needed and who can I rewrite my application to speed this up by avoiding calls to this slow function?

I am using Vue 2.6.14

[RichardKaufmannOG]

Does this flushCallbacks() depend on the usage of async/await or asynchron behavior in general? So would it be a difference when I use a Promise instead?