Observability
Dark Launching: Testing Persistence and Load Before the Big Reveal
Learn how to use Dark Launching to verify your system's uptime under real production load without exposing new features to users. Monitor your dark code with Watch.dog.
By Watch Dog TeamPublished April 12, 202511 min read
The Silent Battle-Test
Symptom Log
middleware.js
app.use((req, res, next) => {
// Shadow mode: run new logic but don't show result to user
if (Math.random() < 0.1) {
runNewInternalSearch(req.query);
}
next();
});Dark Launching is the practice of shipping code to production but keeping it 'dark' (hidden from the UI). This allows the code to process real production traffic or background tasks to see how it affects system latency and database load.
Without Dark Launching, a new feature launch is often a 'guess' that can result in an accidental DDoS of your own database.
Watch.dog Visibility
Configure Watch.dog Shadow Monitors to track the error rate and response time of your 'dark' endpoints. If the dark code starts failing, our system will alert you before it ever touches a real user.
Fix Verification
shadow_impact.log
[INFO] Dark Launch Active (10% traffic).
[WARNING] Origin DB Latency increase: +150ms.
[WATCH.DOG] ALARM: Shadow Endpoint P99 reached 2000ms.
[ACTION] Disabling dark-launch toggle to protect production.Zero-Risk Innovation
Dark launching allows your engineering team to move faster and deploy with confidence, knowing that 'Up' is guaranteed by Watch.dog's external sentinels.
Deployment Comparison
| Type | User Visibility | Watch.dog Focus |
|---|---|---|
| Full Deploy | 100% | Global Availability |
| Canary | 1-5% | Comparison metrics |
| Dark Launch | 0% | Back-end Stress & Latency |
The best outages are the ones that only happened in the dark.