Yes, we looked at Renjin and it's just not what we want, they re-implemented R based off 2.14 and don't do feature parity with that version or newer versions and since the actual analytics code is developed in vanilla R it didn't seem attractive. Also this was a few years back and Renjin as is has sparse documentation and seemingly not too many users and back then the situation on those fronts was worse. To the instance question, I simply mean spinning up a N-amount (usually 4-6) of R processes (there are multiple apps and hundreds of users so we couldn't make it a single linear queue for processing). We mainly use it for optimization calls so we prime the optimization engine in R with the required packages etc and then the R processes just lingers around ready to do an optimization when required.