F# does not have impicit type conversions and so the following code doesn't compile:

let cache = redisConnection.GetDatabase()
cache.StringSet( "Server", server) // compile error

In StackOverflow you can find a workaround by introducing a custom operator and using SRTPs (statically resolved type parameters).

This actually works, but is far from being nice ootb experience. Can you please add an explicit conversion function or a ctor to convert from string to RedisKey?