206 caching can now be done natively with nginx mainline

[ti-mo]

Just in case some people are still implementing this project (or some of its forks): one http request can now be split into multiple parts called 'slices', and thus multiple cache keys using the slice module

This has been available since mainline 1.9.8 and was originally implemented in Tengine. A complete configuration guide can be found on the Nginx Admin Guide.