# What Is Traffic Mirroring?

> Traffic mirroring sends a copy of live requests to a second service for testing while the original still serves the response, so the mirror has no user impact.

Source: https://latchkey.dev/learn/ci-glossary/traffic-mirroring-definition  
Updated: 2026-06-26

## Why it matters

Mirroring is a safe way to validate a new release against production traffic patterns in a deploy pipeline. It catches regressions that synthetic tests miss without risking user-facing errors.

## Where this shows up in a real pipeline

A definition is only useful if you can recognise the thing in your own logs. In practice this concept surfaces when a job behaves differently between a local run and a runner, which is where most CI debugging starts.

- Compare a local run against a CI run of the same command before assuming a tool is at fault.
- Runner environments differ in shell, PATH, TTY availability, available memory, and disk. Most CI-only behaviour traces to one of those five.
- Pin tool versions so an environment difference cannot be introduced by an unrelated update.

## FAQ

### What is What is traffic Mirroring??

Traffic mirroring, also called shadowing, duplicates real production requests and forwards the copy to another version of a service while the primary continues to handle the actual response. The mirrored responses are discarded, so users are unaffected. It lets you exercise a new build with realistic load before it serves anyone.

### Why does What is traffic Mirroring? matter in CI/CD?

Mirroring is a safe way to validate a new release against production traffic patterns in a deploy pipeline. It catches regressions that synthetic tests miss without risking user-facing errors.

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Latchkey runs CI/CD that repairs its own failures. Agent entry points: https://latchkey.dev/agent.txt, https://latchkey.dev/openapi.json, https://latchkey.dev/llms.txt