My initial reaction as well was to suggest a DB like MySQL, but on further consideration... I've worked on a website with over 8000 entries where each entry had about 15 pieces of metadata, all of which was stored in DBMs. It's worked reliably for over five years.
Question to the questioner: is this the first brush at this sort of system that your employer has attempted? If so, don't try to get it perfect, just get something out there that works, even if you end up rewriting the whole thing again in 6 months. It's unavoidable that the requirements will change, and it's futile to spend time now implementing a heavyweight architecture where the problem domain isn't clear.