K6 is a popular load testing tool but it does have limitations at each of the different subscription levels. Let’s take a look at some of the K6 limitations that are in place and what it will cost if you need higher limits.
For the $99/month subscription, you can load test 100 virtual users. That’s not that much. And the test can only run 15 minutes. That’s not much of a load test. And they’ll save your data for one month. One of the keys to load testing is to see how results have changed over time. Not if you’re using k6. And no usage reports with that.
For the $499/month subscription, it’s not much better. You’re now paying 5 times more and your test can only be 30 minutes. You can test 1,000 virtual users, but that’s less than what many people need.
Which means you’ll have to pay $1,499/month. And now you can load test 3,000 virtual users. And you finally can integrate your load testing with your APM.
But if you want usage reports or SAML, you’re starting at $25,000/year.
If you need to run larger tests, that starts at $999 to run larger tests, say a 10,000 virtual user test. That’s in addition to what you’re already paying. And you can only run 5 of them. If you want to run 100,000 virtual user tests, that will be $3,999 for 5 tests.
If you want to run soak tests of say 8 hours, it will be $999 for each 10,000 virtual user test you run. And if you want to run it for 24 hours, it is $2,749 per test.
How does that compare to RedLine13? RedLine13 has a free subscription that has higher limits than paid K6 subscriptions. And the RedLine13 free subscription doesn’t expire. It’s not a trial. There are users that have been using the free subscription for years because that’s all they need. The free subscription has no limit on the number of tests. You can’t even get that with the K6 $1,499/month subscription. And the maximum test duration for a RedLine13 free subscription is 24 hours. That is $2,749 for just one 24 hour test on K6. The RedLine13 free subscription has a limit of 10 vCPUs. Don’t confuse that with K6 VUs. AWS uses vCPU to measure the size of their cloud servers. The number of virtual users you can run depends on the specifics of your load tests, but you can run real tests.
RedLine13 has a paid subscription for $75/month. And that has a limit of 50 vCPUs and no limit on the test duration. There is also a $299/month and a $499/month subscription detailed here.
Here’s a table which highlights some of the key limitations.
| K6 | RedLine13 | |
| $99/month | $75/month* | |
| Virtual Users | 100 | Much higher than 100 – 50 vCPU limit |
| Test Runs/Month | 50 | Unlimited |
| Test Length | 15 minutes | Unlimited |
| $499/month | $299/month* | |
| Virtual Users | 1,000 | Unlimited |
| Test Runs/Month | 75 | Unlimited |
| Test Length | 30 minutes | Unlimited |
| $1,499/month | $499/month* | |
| Virtual Users | 3,000 | Unlimited |
| Test Runs/Month | 100 | Unlimited |
| Test Length | 30 minutes | Unlimited |
| 8 hour 10,000 Virtual User Tests – 5 | $999 additional cost | No additional RedLine13 cost, minimal AWS cost |
| 24 hour 10,000 Virtual User Tests – 5 | $2,749 additional cost | No additional RedLine13 cost, minimal AWS cost |
*AWS costs when using RedLine13 are very low even when running large tests. There are many articles that explain what to expect for AWS costs and examples of how little it is.