SELECT 
  product_id, 
  group_id 
FROM 
  cscart_product_variation_group_products 
WHERE 
  group_id IN (
    46, 119, 120, 142, 128, 144, 145, 44, 39, 
    40, 132, 133, 129, 121, 127, 126, 47, 
    125, 123
  )

Query time 0.00044

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "78.72"
    },
    "table": {
      "table_name": "cscart_product_variation_group_products",
      "access_type": "index",
      "possible_keys": [
        "idx_group_id"
      ],
      "key": "PRIMARY",
      "used_key_parts": [
        "product_id",
        "group_id"
      ],
      "key_length": "6",
      "rows_examined_per_scan": 379,
      "rows_produced_per_join": 61,
      "filtered": "16.09",
      "using_index": true,
      "cost_info": {
        "read_cost": "66.53",
        "eval_cost": "12.20",
        "prefix_cost": "78.73",
        "data_read_per_join": "976"
      },
      "used_columns": [
        "product_id",
        "group_id"
      ],
      "attached_condition": "(`cscart`.`cscart_product_variation_group_products`.`group_id` in (46,119,120,142,128,144,145,44,39,40,132,133,129,121,127,126,47,125,123))"
    }
  }
}