Viewing <https://wikitech.wikimedia.org/wiki/Incident_documentation/20190407-Zotero> as logged-out shows a cached copy of a mobile view.
This suggests that the "Mobile view" switch, or the UserAgent-based switcher in VCL, is nor fragmenting the cache in Varnish for this domain.
```
age: 38142
backend-timing: D=150221 t=1554815686837695
cache-control: s-maxage=86400, must-revalidate, max-age=0
content-encoding: gzip
content-language: en
content-type: text/html; charset=UTF-8
date: Tue, 09 Apr 2019 23:50:30 GMT
last-modified: Tue, 09 Apr 2019 10:21:20 GMT
server: labweb1001.wikimedia.org
server-timing: cache;desc="hit-front"
set-cookie: WMF-Last-Access=09-Apr-2019;Path=/;HttpOnly;secure;Expires=Sat, 11 May 2019 12:00:00 GMT
status: 304
strict-transport-security: max-age=106384710; includeSubDomains; preload
vary: Accept-Encoding,Cookie,Authorization
via: 1.1 varnish (Varnish/5.1), 1.1 varnish (Varnish/5.1), 1.1 varnish (Varnish/5.1)
x-analytics: ns=0;page_id=443776;https=1;nocookies=1
x-cache: cp1087 hit/1, cp3040 hit/1, cp3040 hit/2
x-cache-status: hit-front
x-content-type-options: nosniff
x-powered-by: HHVM/3.18.6-dev
x-varnish: 600819990 545850611, 255861948 429783245, 318755371 354620612
```