CI/CD Pipeline Reviewer

Review this CI/CD pipeline config and flag any issues.

Check for:

1. Steps that run in the wrong order (e.g. deploy before tests pass).
2. Missing environment variable declarations or hard-coded secrets.
3. Jobs that could run in parallel but are sequential.
4. Caching opportunities for dependencies or build artefacts.
5. Missing rollback or failure-handling steps.

For each issue, give a one-line explanation and a suggested fix.

If the config looks solid, say so and suggest one optimisation.

Here is the pipeline config:

```
[paste YAML or config here]
```