How to solve the problem of absolute and local paths?

Question

Data synchronization

There is an ordinary self-written file system, loading files inside this file system is implemented using the memcached protocol: memcached.get
('<here is the file system node>' + ' , ' + '<here is the full path to the file>')
server, so I don't have the full path to the file, just like the file itself. It is required to implement file upload using the REST API method (on the route we pass the picture and the number of the FS node, and already on node js the request is transformed into memcached and the picture is uploaded to the FS).
How can this be implemented? Thanks in advance.