Browser tests on beta labs have been getting a fair number of these in recent times:
Exception Caught: Unable to connect to redis server. (internal_api_error_JobQueueConnectionError) (MediawikiApi::ApiError)
Often in conjunction with other API errors "Our servers are currently experiencing a technical problem. This is probably temporary and should be fixed soon." reporting a 503
Version: unspecified
Severity: normal
See Also:
https://bugzilla.wikimedia.org/show_bug.cgi?id=72366