hardRequests a second, what one instance does, a burst and a timeout: the arithmetic that says how many instances — and why the answer changes once one of them is allowed to die.
load balancer
service
capacity planning
bursts and queues
utilisation
N+1
0 of 5 done
1Read the numbers
client_web
Web client
load: 100–140 requests a minute; 4 a second for 6 s after the newslettertimeout: gives up after 10 s
load_balancer
Load balancer
service×2
Export service
instances: 2latency: 1 s per request, one at a time per instancequeue: up to 12 waiting per instance
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An export service sits behind a load balancer, and every figure it needs is on the diagram. At the busy end of the evening 140 requests a minute arrive. One instance handles a request in one second, one at a time, and queues up to 12. Clients give up after 10 seconds. It runs two instances. What happens at the busy end?