Laravel forbid updating row if its referenced in another table

say Table A and Table B (table B has a foreign key a_id) I want to be able to update a row in A as long as it's not ref in B I already did it but I'm looking for a better approach.

My approach

$referencesInB = TableB::where('a_id', $id)->exists();
if ($referencesInB) {
    return response()->json(['error' => 'Cannot update'], 403);
}
$rowA->update($request->all());

$referencesInB = TableB::where('a_id', $id)->exists();

You can avoid the extra query check above(saving us a few milliseconds or more) by eager loading the relation and checking if the relation actually loaded. So, it all happens with 1 query instead of 2 eliminating the N + 1 query issue docs.

<?php

$rowA = TableA::with('table_b')->find($id);

if ($rowA->relationLoaded('table_b')) {
  return response()->json(['error' => 'Cannot update'], 403);
}

$rowA->update($request->all());