Mediumsystem-designqueueasync

A queue for notifications

Acceptance: —Solved by: 0

Statement

A notification service: normally 600 requests/s, half of them writes. Once a day traffic grows 6× for 20 seconds (a push campaign): 1800 writes per second, i.e. 5400 database units — no tier takes that. Route the writes through a message queue: users get an instant reply and workers drain the queue into the database at 200 messages/s per instance. Mind two things: the queue must be empty by the end of the scenario, and workers must not write faster than the database can absorb.

Constraints

p95 ≤ 250 ms, errors ≤ 0.1 %, queue empty by the end, budget $2800/month, ≤ 5 instances per node.

Requirements

SimulationBuild from scratch

p95

≤ 250 ms

Errors

≤ 0.10 %

Budget

$2,800/mo

Users

200,000

Your architecture costs$0 / $2,800

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

Scenarios (checked in order)

1A normal dayLoad
600 requests/s for 60 seconds: 40 % reads, 50 % writes, 10 % static.
60 s · 600 rps · R 40 / W 50 / S 10 %
2Push campaignSpike
From second 20, traffic grows 6× for 20 seconds (3600 requests/s); the queue must drain within the 120 seconds.
120 s · 600 rps · R 40 / W 50 / S 10 % · ×6 from s 20 for 20 s

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