My custom Drupal 7 to Drupal 8 migration correctly follows dependencies and first migrates users, then articles. The problem is that it fails to import user IDs into the 'uid' field and leaves it at '0'. For uid processing, I use the following YAML snipped. Note that 'luxus_users' is the user migration that works fine.
process: uid: plugin: iterator source: uid process: target_id: plugin: migration migration: luxus_users source: uid
I hoped would work for me as similar one for file migration already works for me.
field_logo: plugin: iterator source: field_logo process: target_id: plugin: migration migration: luxus_files source: fid