It may be useful to see what Nix does.
Nix has many static id, with the comment:
# IMPORTANT!
# We only add static uids and gids for services where it is not feasible
# to change uids/gids on service start, in example a service with a lot of
# files. Please also check if the service is applicable for systemd's
https://github.com/NixOS/nixpkgs/blob/master/nixos/modules/misc/ids.nix