$ curl -si -X GET /Zq9Zq9
HTTP/1.1 404 
{"detail":"no such code: Zq9Zq9","instance":"/Zq9Zq9","status":404,"title":"Not Found"}

$ curl -si -X GET /Zq9Zq9
HTTP/1.1 404 
{"detail":"no such code: Zq9Zq9","instance":"/Zq9Zq9","status":404,"title":"Not Found"}

cache misses: before=2 after-first-404=3 after-second-404=3
$ redis-cli GET url:Zq9Zq9   # the negative-cache marker
-
$ redis-cli TTL url:Zq9Zq9
60