Does Contao fall back to the filesystem cache driver when no external cache is configured?

The goal is to understand why a Contao installation that operates correctly with the filesystem cache on a developer's machine fails after deployment to a production server, even though no explicit cache configuration has been changed.

In the local environment Contao appears to default to the filesystem cache, but the production server may be selecting a different driver based on environment variables, installed extensions, or version‑specific defaults, leading to unexpected errors or silent fallback failures.

Which cache driver does Contao actually use when no driver is explicitly set? Does the presence of variables such as CONTAO_CACHE_DRIVER or CONTAO_CACHE_PREFIX override the default selection? How can the active driver be confirmed in each environment without altering the application code?