Thread Safe as a database?

[proyb6]

What data format is the .db store in?

Is it thread safe for used in web server?

Is it possible to store Chinese, Japanese and non-Latin with escaped characters?

Is there a maximum length per rows I could store e.g. probably up to 20,000 characters?

Is it possible to keep new data or fresh data in Vedis's memory (for performance) until it hit the threshold and offload to disk while the in-memory will continue to be use for frequent access?