Security: Does router.invalidate() delete cache data?

[leovigna]

According to react/guide/data-loading
"router.invalidate() will force all active routes to reload their loaders immediately and mark every cached route's data as stale."

Does marking the cache as stale mean all data is deleted or does it just mark the keys as stale? I would assume the former but just wanted to make sure as I am not familiar with the cache implementation.