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Reliability and performance tests

Soak test

1 min

Intro

Soak test (also called endurance test) evaluates system performance over an extended period under a typical or expected load. The goal is to detect issues like memory leaks, resource exhaustion, or performance degradation that appear only after prolonged usage.

 
Easy explanation

Checking if a bridge stays safe and stable after carrying traffic for many hours.

Scheme

Soak test scheme

 
Info

To better understand the terms in testing and tool k6 see vocabulary.

Key characteristics

  • Sustained load: Keeps the system at a steady level of typical or peak expected traffic.
  • Long duration: Focus on detecting slow degradation over hours.
  • Stability focus: Identifies issues like memory leaks, gradual performance decline, and unreleased resources.
  • Operational realism: Simulates long-running production-like conditions.

Practical examples

  • Does the system remain stable after handling 500 users for 8 hours?
  • Are there signs of memory exhaustion or degraded response times after prolonged execution?

Users and time

  • Number of virtual users:

    Simulates typical load (e.g., 500 users) for extended periods.

  • Execution time:

    4–8 hours or longer, enough to expose resource-related issues.

Example with tool k6

script.js 

import http from 'k6/http';
import { check, sleep } from 'k6';

export const options = {
  stages: [
    { duration: '5m', target: 500 }, // ramp-up
    { duration: '8h', target: 500 }, // hold steady load
    { duration: '5m', target: 0 }, // ramp-down
  ],
  thresholds: {
    http_req_failed: ['rate<0.01'],
    http_req_duration: ['p(95)<1000'],
  },
};

export default function () {
  const response = http.get('https://api.example.com/products');

  check(response, {
    'status is 200': (res) => res.status === 200,
  });

  sleep(1);
}
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