I have some concerns about this; I know from the past that `call()` and `apply()` have had performance issues compared to calling directly. I don't know what the perf profile of v8 is but it's possible that it would be more efficient to just pass `this` as a first argument to the function and amend the functions accordingly--or, pass in both `this._keyEncoding` and `this._valueEncoding` as the first 2 parameters always.

Thoughts? Any idea what perf is like in v8 these days for `call()`?