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# Why Your Docker Build Reinstalls Every Dependency Every Time
- URL: https://debugly.dev/docker-layer-cache-invalidation/
- Published: 2026-08-29T09:00:00.000Z
- Updated: 2026-10-17T05:49:05.000Z
- Description: One changed byte early in a Dockerfile throws away everything after it. Here is how the cache key is computed and how to order instructions so it survives.
- Author: Rohit Bhadani
- Tags: Docker, Deep Dive, DevOps, Performance

| Instruction | Key includes                                   |
| ----------- | ---------------------------------------------- |
| RUN         | The literal command string, not its effects    |
| COPY / ADD  | Contents and metadata of the files copied      |
| ENV, ARG    | The value, and it invalidates everything after |
| FROM        | The resolved image digest                      |

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Published on [debugly.dev](https://debugly.dev/) by [Rohit Bhadani](https://debugly.dev/about/) | Founder of [Krova Cloud](https://krova.cloud/?ref=debugly.dev)