SELECT 
  product_id, 
  group_id 
FROM 
  cscart_product_variation_group_products 
WHERE 
  group_id IN (
    31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 
    42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 
    52, 53, 54
  )

Query time 0.00020

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost": 0.02849248,
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_product_variation_group_products",
          "access_type": "range",
          "possible_keys": ["idx_group_id"],
          "key": "idx_group_id",
          "key_length": "3",
          "used_key_parts": ["group_id"],
          "loops": 1,
          "rows": 48,
          "cost": 0.02849248,
          "filtered": 100,
          "attached_condition": "cscart_product_variation_group_products.group_id in (31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54)",
          "using_index": true
        }
      }
    ]
  }
}

Result

product_id group_id
13439 31
13467 31
13440 32
13468 32
13441 33
13469 33
13442 34
13470 34
13443 35
13471 35
13444 36
13472 36
13445 37
13473 37
13446 38
13474 38
13447 39
13475 39
13448 40
13476 40
13449 41
13477 41
13450 42
13478 42
13451 43
13479 43
13452 44
13480 44
13453 45
13481 45
13454 46
13482 46
13455 47
13483 47
13456 48
13484 48
13457 49
13485 49
13458 50
13486 50
13459 51
13487 51
13460 52
13488 52
13461 53
13489 53
13462 54
13490 54