Flush function enhancement

### What

The current flush function, which writes storage content from RAM to the storage file is synchronous. I am opening this task to discuss whether it can be made asynchronous instead of synchronous.

### Acceptance Criteria (DoD)

- Decide if flush will sync or async
- if async choosed implementation should be provided.

### How

_No response_

The issue does not name a file, test, or entry point. Start by locating the current flush function and tracing how RAM content is written to the storage file; then review the surrounding storage API before deciding whether synchronous or asynchronous behavior is appropriate. Done means the decision is documented, with an implementation and tests if asynchronous behavior is chosen.

Written by the indexing model from the issue text.