Do we still have 16 MB document size limitation? Or Is there any workaround to store a document size more than 16 MB?
You can absolutely change this with a simple change to the source
code, however as many parts of MongoDB Community and Percona Server for MongoDB expect this limit to exist you may run into odd race conditions or error when exceeding this size. Before undertaking such a drastic change, I would ask what your trying to solve for that DBRef, $lookup, gridFS, aggregations $out, and other such functionality does not provide for you.