If you’re in QA, you know these two show up more reliably than your actual team sometimes. Error 429 (Too Many Requests) and Error 500 (Internal Server Error) are your daily companions. But they don’t just show up anywhere, they show up in the places that matter most.
Why Checkout Is Where 429s Live
Testing a basic CMS page? You’re probably not going to see a 429. Those pages are mostly static, cached, low stakes. A user reads some content, maybe clicks around. The server doesn’t break a sweat.
But checkout or cart pages? That’s the easiest example of where QAs consistently hit 429s.
Here’s why. Payment gateway integrations. Whether it’s hosted fields, custom built forms hitting payment APIs, or any combination of validation, authorization, and processing calls, checkout flows are making multiple API requests to different services.
And there are millions of ways these integrations can go wrong. The API calls fire simultaneously without proper throttling. The async handling breaks. The integration itself is just implemented incorrectly.
The result? 429s. All the time.
Even if it “works on my machine” with one test, QA hits these errors constantly because we’re actually running through the flows repeatedly.
Side note: We covered HTTP status codes in detail in our manual API testing post. These codes aren’t limited to API testing, you’ll see them constantly when you fire up dev tools in the browser. 404s, 402s, CORS errors, 500s. They’re everywhere.
The QA Catch-22
So you’re testing checkout. You need to verify the payment flow actually works. Here’s what happens.
Test the flow repeatedly (because that’s your job), you hit 429 because you slammed the API rate limit. Test conservatively, spacing out attempts, you get 500 because you miss the timing issues, race conditions, or intermittent failures.
Can’t win.
But here’s the thing, this is exactly what we’re supposed to find. These errors aren’t obstacles. They’re showing you where the system breaks before real users find out during a sale.
The “Works on My Machine” Response
You come back with errors from your test runs.
You: “Getting consistent 429s during checkout testing”
Dev: “Works on my machine”
You: “How many times did you test it?”
Dev: “Once. Went through fine.”
You: “Right, but I’m hitting rate limits after multiple test runs. If QA triggers this easily, real users will too.”
Dev: “That’s not realistic” or “Must be your setup”
You persist with logs and screenshots.
Dev: “Don’t start drama”
Sound familiar?
The Professional Response
Frame it correctly. “No offense, these are the errors I encountered. This is actually a good thing, we’re catching this before production.”
Still get pushback? Don’t argue with devs directly. Escalate to their manager. This isn’t drama, it’s preventing actual production fires.
For QA Leads: Protect Your Team
When junior QAs face “works on my machine” dismissals, step in immediately. Talk to management, not the dev. Keep the chain of command clean. Create that paper trail.
This is building influence without stepping on others, you’re maintaining standards through proper channels.
The Data Driven Approach
Structured pushback uses evidence nobody can ignore. Screenshots of 429 responses. Network logs from dev tools. Reproducible steps. Business impact: “This affects checkout under normal testing loads, which means it’ll affect real users.”
Don’t say: “I think there’s an issue”
Say: “We hit 429s after X checkout attempts. Here are the network logs showing the rate limit responses from the payment gateway.”
Why These Errors Matter
429s and 500s in testing are success stories. Every 429 you trigger is one you prevented in production. Every 500 you catch is a customer who won’t abandon their cart. Every “works on my machine” pushback you handle protects the business.
Your job isn’t to make devs feel good. Your job is to catch bugs before customers can’t give the company money.
The Reality Check
429s and 500s show you where systems break. “Works on my machine” tested once isn’t QA testing repeatedly. Finding bugs isn’t drama, it’s the job. Data driven feedback is survival.
This is what the QA villain origin story looks like in daily testing. While that article covers the bigger picture of being the person who breaks things, 429s and 500s are the technical proof.
So yeah, 429 and 500 are my best friends. They show up every day, and I wouldn’t have it any other way.
Because better me than production users.
Related Reading:
- Why QA Teams Are Seen as Villains (And Why That’s the Job)
- Making Tough Calls as a QA Lead
- Pushback in QA: Why Saying “No” Saves Projects
QA Overlord, Head of QA
I see 429s and 500s more often than my actual team. Been running checkout tests long enough to know payment gateway integrations break in a million creative ways. I don’t just find these errors, I escalate them properly so junior QAs don’t get steamrolled by “works on my machine” pushback.
Writing at QAJourney.net about the daily reality of QA leadership, making tough calls, and why catching bugs before production isn’t drama, it’s the job.
