There are 2 billion total users. DAU is 1 billion.
Each user will browse 10 videos per day.
Throughput
# Daily video playing number:
1 * 10^9 * 10 = 10 ^ 10
# Video play QPS
10 ^ 10 / 86400 = 10 ^ 5
# Assume each user watches 5 minutes, simulatenously watched videos
10^5 * 5 * 60 = 3 * 10^7
# Upload QPS
# Assume each video will be played 200 times, then the upload QPS should be
10^5 / 200 = 500
# Suppose each video is 100 MB
# Then each second, the amount of video uploaded is
100 MB * 500 = 50 GB
# The space needed per year
50GB * 86400 * 365 = 50 * 10^9 * 32 * 10^6 = 1600 PB
# And each video needs 3 backups to avoid loss
1600PB * 3 = 5200PB