SELECT 
  addon 
FROM 
  cscart_addons 
WHERE 
  unmanaged = 1 
  AND status = 'A' 
ORDER BY 
  priority

Query time 0.00015

JSON explain

{
  "query_block": {
    "select_id": 1,
    "nested_loop": [
      {
        "read_sorted_file": {
          "filesort": {
            "sort_key": "cscart_addons.priority",
            "table": {
              "table_name": "cscart_addons",
              "access_type": "ALL",
              "rows": 76,
              "filtered": 100,
              "attached_condition": "cscart_addons.unmanaged = 1 and cscart_addons.`status` = 'A'"
            }
          }
        }
      }
    ]
  }
}