Thanks for the tip, just enabled it.
In the current form, I don't directly deal with stale reads. But there is a CheckExpiry [1] method that iterates thru each cached partition, does a HEAD request to the corresponding S3 object and compares Last-Modified. If the cached object is older than the one in S3, the cache will be invalidated. Currently the user needs to invoke this by them-self.
I also plan on having a user configurable TTL per partition, so user could use low TTL for objects they expect to change, i.e. One would think data for today might change soon, but data from 5 years ago wont.
[1] https://godoc.org/github.com/turbobytes/infreqdb#DB.CheckExp...