Not sure that this is the best answer, but seems like a good use of feature flags. If the flag points to the old state, serve the old assets. If it points to th

Not sure that this is the best answer, but seems like a good use of feature flags. If the flag points to the old state, serve the old assets. If it points to the new state, serve the new assets. So make a deploy with both assets, deploy everywhere, then flip the flag. A bit unsatisfying because it probably isn't always easy the include both assets. Another idea (not sure if a good one) would be having the load balancers pin a certain session to a certain backend machine. Seems like this would make it better without fixing it, though: that session will still need to switch to a different set of assets when "their" server is deployed.