db.js

// event emitter

var waits = 0;
var done = false;

db.on('data', async data => {
  waits++;
  await processData(data);
  waits--;
  if(done)
    if(waits == 0)
      weAreDone();
});

db.on('end', () => done = true);

// stream

async processStream(stream)
{
  while(let data = await stream.read())
  {
    // process data
  }
}

db.on('end', () => stream.close());
await Promise.all[
  processStream(db),
  processStream(db),
  processStream(db)
];