Looking at your nodejs GridStore functionality, it appears that there's an opportunity to increase the functionality of the GridStore.

Currently, if you upload a file to mongo through GridStore, and another process wants to download that file, then it has to wait for the entire upload to complete, before it starts the download. The way the data is stored in the database, this isn't necessary. If fs.files contains information about the content length, then the download process could just continually pull in the data as it gets uploaded, allowing for a quicker downstream process.

I may create a separate nodejs module that handles this downloading, but you may want to consider adding it to your library.