SELECT 
  product_id, 
  group_id 
FROM 
  cscart_product_variation_group_products 
WHERE 
  group_id IN (
    345, 418, 252, 681, 155, 466, 666, 353, 
    381, 212, 266, 664, 383, 648, 432, 373, 
    382, 673, 689
  )

Query time 0.00049

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "36.26"
    },
    "table": {
      "table_name": "cscart_product_variation_group_products",
      "access_type": "range",
      "possible_keys": [
        "idx_group_id"
      ],
      "key": "idx_group_id",
      "used_key_parts": [
        "group_id"
      ],
      "key_length": "3",
      "rows_examined_per_scan": 70,
      "rows_produced_per_join": 70,
      "filtered": "100.00",
      "index_condition": "(`softwarepirmam_hewadelivard_cscart_4`.`cscart_product_variation_group_products`.`group_id` in (345,418,252,681,155,466,666,353,381,212,266,664,383,648,432,373,382,673,689))",
      "cost_info": {
        "read_cost": "29.26",
        "eval_cost": "7.00",
        "prefix_cost": "36.26",
        "data_read_per_join": "1K"
      },
      "used_columns": [
        "product_id",
        "group_id"
      ]
    }
  }
}