One headache I had in the past was with a highly-available app with stored procs. It was rare to do parallel app server restarts, they were instead done in seri

One headache I had in the past was with a highly-available app with stored procs. It was rare to do parallel app server restarts, they were instead done in serial. (This did make certain migrations a pain.) Outdated app servers would continue calling pgpgsql functions in the outdated way until they received new code. We solved it with a small wrapper around the calls to plpgsql functions — we set up a build process to generate unique names that were called by version. During deploy, we'd have two or more versions of the 'same' function running in parallel. The last deploy step dropped the now-outdated functions. It worked relatively well.