gistfile1.txt

var redis = require('redis')
var cache = redis.createClient()

var subjectQueryParams = {'_id': 0, 'school_state': 1, 'resource_type': 1, 'poverty_level': 1, 'date_posted': 1, 'total_donations': 1, 'funding_status': 1, 'grade_level': 1}

var getSubjects = function(done) {
     cache.get('subjects', function(err, data){
        if(err) return done(err)
     if(data)
       return done(null, JSON.parse(data))
     Subjects.find({}, subjectQueryParams, function(err, results) {
       if(err) return done(err)
       if(results) {
         cache.set('subjects', JSON.stringify(results))
       }
       done(null, results) // no results
    })
  })
}

app.get('/api/data', function(req, res) {
 getSubjects(function(err, data) {
   if (err) return res.send(err);
   res.json(data); 
});

Also, might want to consider using promises