Check out this podcast which details the experience of working at a Amazon FBA warehouse:
https://www.ecomcrew.com/e161-what-i-learned-while-working-at-an-amazon-fba-warehouse/
Interesting to note the presenter say that there wasnt much automation in place.
Also, throughput of 600 items per picker per hour & 50 oversize items per hour.
Regards
dim81