A fast worker
Definition 1 of 2
Pro Tip 1/3Work Context
Use 'a fast worker' for someone who performs job tasks quickly and well. 
During the inventory, our team realized Sheila is a fast worker.
Pro Tip 2/3Positive Evaluation
'A fast worker' is often a compliment in professional settings, showing respect. 
Our manager always praises Paul because he's a fast worker.
Pro Tip 3/3Potential Ambiguity
Sometimes 'a fast worker' might imply careless work, so context matters. 
He's a fast worker, but check his work for errors.