Easysystem-designload-balancingscaling

Load balancer

Acceptance: 100.0%Solved by: 1

Statement

The product has grown: normal load is now 1200 requests per second and evenings bring twice that. One “app server” node may hold at most 5 instances (an organisational limit), so you need several server groups with a load balancer in front. The load balancer splits requests evenly across the app servers attached to it. Pick the database tier for the load: a write costs 3× a read.

Constraints

p95 ≤ 300 ms, errors ≤ 0.1 %, budget $2400/month, ≤ 5 instances per node.

Requirements

SimulationBuild from scratch

p95

≤ 300 ms

Errors

≤ 0.10 %

Budget

$2,400/mo

Users

100,000

Your architecture costs$0 / $2,400

★ within budget · ★★ ≤ 75 % · ★★★ ≤ 50 % of the budget

Scenarios (checked in order)

1Daytime loadLoad
1200 requests/s for 60 seconds: 80 % reads, 10 % writes, 10 % static.
60 s · 1,200 rps · R 80 / W 10 / S 10 %
2Evening peakSpike
From second 30, traffic doubles for 60 seconds (2400 requests/s).
120 s · 1,200 rps · R 80 / W 10 / S 10 % · ×2 from s 30 for 60 s

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