Sale day capacity
A shop normally gets 2,000 requests per second. On sale day it gets 10,000. One app server handles up to 800 requests per second and costs $60 a month; the monthly budget for app servers is $1,000. The load balancer spreads requests evenly. The shop must survive the sale-day peak even if one server dies during it. Choose the smallest number of servers that does all of this.
2,000requests/s on a normal day
10,000requests/s at the peak
800requests/s one server handles
$60per server per month
$1,000monthly budget
3
Monthly cost
How the numbers work out:
- At the peak you need 10,000 ÷ 800 = 12.5 servers, so 13.
- One of them may die, and the other 13 must still carry the peak: 13 + 1 = 14.
- 14 × $60 = $840 a month, inside the $1,000 budget.
- 13 servers would hold the peak until one dies: then 12 × 800 = 9,600 requests per second, short of 10,000. 15 or more still works, but you pay for servers you don't need.