How to load field configurations in code
The terminology is a bit confusing (as usual with Drupal), but here goes:

Field storage configurations are defined by FieldStorageConfig. To load one, do this:

$field = Drupal::entityTypeManager()-&gt;getStorage('field_storage_config')-&gt;load('node.my_field');


Field instance configurations are defined by FieldConfig. To load one, do this:

$field_instance = Drupal::entityTypeManager()-&gt;getStorage('field_config')-&gt;load('node.my_content_type.my_field');