In T422112#11860469, @phuedx wrote:

1. There are two flaws in the design of the cache/stash update strategy:
   1. <snip />
   2. We only invalidate the cache if the value of the stash is out of date. Therefore, it's possible that an invalid/out of date value could get stuck in the cache as long as the value in the stash is up to date (e.g. a new experiment is configured in Test Kitchen UI). If the maintenance script doesn't invalidate the cache, it should be updated on a cache miss followed by a read from the stash.

AC

• ConfigsFetcher#updateConfigs() checks whether the cached value is out of date and, if so, updates it
• ConfigsFetcher#updateConfigs() checks whether the stashed value is out of date and, if so, updates it
• Test by taking the current configuration from the stash, adding a fake experiment, writing that to the cache and watch for it to be invalidated & removed in about a minute.