SELECT 
  f.feature_id, 
  f.purpose, 
  p.product_id, 
  p.parent_product_id, 
  g.id, 
  g.code 
FROM 
  cscart_product_variation_group_features AS f 
  INNER JOIN cscart_product_variation_groups AS g ON f.group_id = g.id 
  INNER JOIN cscart_product_variation_group_products AS p ON f.group_id = p.group_id 
WHERE 
  p.product_id IN (
    3484, 3487, 3485, 3486, 6969, 3434, 6947, 
    3424, 3911, 3422, 3910, 3421, 3909, 
    3420, 3423, 3912, 3914, 3913, 3433, 
    3432, 3135, 3403, 3404, 3405, 3406, 
    3408, 3409, 6930, 6931, 6932, 6933, 
    6934, 6935, 6936, 3407, 2666, 3845, 
    2667, 2668, 2669, 2670, 3846, 3847, 
    3848, 3849, 3850, 6258
  )

Query time 0.00055

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "98.71"
    },
    "nested_loop": [
      {
        "table": {
          "table_name": "p",
          "access_type": "range",
          "possible_keys": [
            "PRIMARY",
            "idx_group_id"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "product_id"
          ],
          "key_length": "3",
          "rows_examined_per_scan": 47,
          "rows_produced_per_join": 47,
          "filtered": "100.00",
          "index_condition": "(`gaseus`.`p`.`product_id` in (3484,3487,3485,3486,6969,3434,6947,3424,3911,3422,3910,3421,3909,3420,3423,3912,3914,3913,3433,3432,3135,3403,3404,3405,3406,3408,3409,6930,6931,6932,6933,6934,6935,6936,3407,2666,3845,2667,2668,2669,2670,3846,3847,3848,3849,3850,6258))",
          "cost_info": {
            "read_cost": "28.21",
            "eval_cost": "4.70",
            "prefix_cost": "32.91",
            "data_read_per_join": "752"
          },
          "used_columns": [
            "product_id",
            "parent_product_id",
            "group_id"
          ]
        }
      },
      {
        "table": {
          "table_name": "g",
          "access_type": "eq_ref",
          "possible_keys": [
            "PRIMARY"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "id"
          ],
          "key_length": "3",
          "ref": [
            "gaseus.p.group_id"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 47,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "11.75",
            "eval_cost": "4.70",
            "prefix_cost": "49.36",
            "data_read_per_join": "18K"
          },
          "used_columns": [
            "id",
            "code"
          ]
        }
      },
      {
        "table": {
          "table_name": "f",
          "access_type": "ref",
          "possible_keys": [
            "idx_group_id"
          ],
          "key": "idx_group_id",
          "used_key_parts": [
            "group_id"
          ],
          "key_length": "3",
          "ref": [
            "gaseus.p.group_id"
          ],
          "rows_examined_per_scan": 3,
          "rows_produced_per_join": 141,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "35.25",
            "eval_cost": "14.10",
            "prefix_cost": "98.71",
            "data_read_per_join": "14K"
          },
          "used_columns": [
            "feature_id",
            "purpose",
            "group_id"
          ]
        }
      }
    ]
  }
}