SELECT 
  product_id, 
  parent_product_id 
FROM 
  cscart_product_variation_group_products 
WHERE 
  product_id IN (146)

Query time 0.00041

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "1.20"
    },
    "table": {
      "table_name": "cscart_product_variation_group_products",
      "access_type": "ALL",
      "rows_examined_per_scan": 7,
      "rows_produced_per_join": 0,
      "filtered": "14.29",
      "cost_info": {
        "read_cost": "1.10",
        "eval_cost": "0.10",
        "prefix_cost": "1.20",
        "data_read_per_join": "15"
      },
      "used_columns": [
        "product_id",
        "parent_product_id"
      ],
      "attached_condition": "(`mobikul_delivery_boy_livedemo`.`cscart_product_variation_group_products`.`product_id` = 146)"
    }
  }
}