SELECT 
  product_id, 
  group_id 
FROM 
  cscart_product_variation_group_products 
WHERE 
  group_id IN (
    829, 847, 824, 828, 836, 826, 825, 845, 
    851, 865, 858, 843, 859, 863, 834, 827, 
    830, 846, 835, 864, 844, 861, 849, 862, 
    850, 833
  )

Query time 0.00069

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "44.76"
    },
    "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": 85,
      "rows_produced_per_join": 85,
      "filtered": "100.00",
      "index_condition": "(`softwarepirmam_hewadelivard_cscart_4`.`cscart_product_variation_group_products`.`group_id` in (829,847,824,828,836,826,825,845,851,865,858,843,859,863,834,827,830,846,835,864,844,861,849,862,850,833))",
      "cost_info": {
        "read_cost": "36.26",
        "eval_cost": "8.50",
        "prefix_cost": "44.76",
        "data_read_per_join": "1K"
      },
      "used_columns": [
        "product_id",
        "group_id"
      ]
    }
  }
}