During analysis for T263043, we noticed that restbase sent varnish responses that were incomplete (which is ok - you want your service to degrade as graciously as possible), but that would also be cached by the upper layers of the infrastructure.

I think it makes sense, when working in degraded mode, to either:

• Signal no caching should happen
• (better) Set maxage to some low (configurable) value

I prefer the latter option as it will prevent a cascading failures propagation (AQS doesn't work, so wikifeeds sends back uncacheable responses -> wikifeeds gets swarmed itself).