At the moment, kartotherian exposes the following HTTP headers related to caching:

• ETag
• Last-Modified (always Thu, 01 Jan 1970 00:00:00 GMT)
• Date

The ETag exposed is inconsistent between the different kartotherian nodes. As such, it should probably just be dropped, or replaced by a ETag that is consistent (a hash of the tile might make sense).

We probably want to have Cache-Control: public, max-age=86400, s-maxage=86400.