The problem with this solution is that it is time consuming, to open file for a key, i would like to use the boost serializeation to improve time preformance.

What is realy required is some mechanism, to identify an instance according to its key and only than read its data. Thus reading only the required instnace (accordig to its key) and not also the previous data at the file, someting like seek.

I hoped that "XML boost" can supply someting like that, but could not find how.