queue.js

var atomicQueue = require(...)

var queue = atomicQueue(db, function (data, cb) {
  console.log('got some work', data)
  // do stuff ...
  cb(null, result) // if no error this work will be removed from the leveldb
})

// write will add this 'work' to the leveldb
queue.write({some: 'world'})

// where there is a work 'result' it will be pushed to the readable stream
queue.on('data', function (data) {
  console.log(data) // the work result
})