hardDesignScenarioMidSeniorStaff
How would you design a test to find where the system breaks, rather than one that confirms it meets its target?
6 min readUpdated 2026-08-15Target archetype: Big Tech, Enterprise Captive, Product Startup
Answer
Short answer
Ramp load steadily past the target until throughput stops rising, record the knee and the collapse point separately, and watch bounded resources such as threads, file descriptors and connection pools, because the first hard limit is often not request rate at all.
Use performance testing as the thread through the testing to find where it breaks explanation: name the signal, then say what changes when it moves.
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Likely follow-ups
- Throughput plateaus but latency keeps climbing and nothing errors. What is happening?
- How would you find a limit that only appears when the fleet scales out rather than up?
- What does a graceful failure past the limit look like, and how would you test that it works?
- The breakpoint is four times your peak traffic. Do you still act on it?
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