SELECT 
  warehouse_id, 
  amount, 
  store_type, 
  position, 
  main_destination_id, 
  pickup_destinations_ids, 
  shipping_destinations_ids, 
  status 
FROM 
  cscart_store_locations AS sl 
  INNER JOIN cscart_warehouses_products_amount AS wpa ON wpa.warehouse_id = sl.store_location_id 
WHERE 
  wpa.product_id = 7434 
ORDER BY 
  sl.position ASC

Query time 0.00099

JSON explain

{
  "query_block": {
    "select_id": 1,
    "read_sorted_file": {
      "filesort": {
        "sort_key": "sl.position",
        "table": {
          "table_name": "sl",
          "access_type": "ALL",
          "possible_keys": ["PRIMARY"],
          "rows": 49,
          "filtered": 100
        }
      }
    },
    "table": {
      "table_name": "wpa",
      "access_type": "eq_ref",
      "possible_keys": ["PRIMARY"],
      "key": "PRIMARY",
      "key_length": "6",
      "used_key_parts": ["product_id", "warehouse_id"],
      "ref": ["const", "admin_test.sl.store_location_id"],
      "rows": 1,
      "filtered": 100
    }
  }
}