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 (
    6843, 6840, 6841, 6846, 13274, 13286, 
    13280, 13292, 3430, 3429, 3437, 3436, 
    3438, 3477, 3452, 3478, 3479, 3453, 
    3491, 3488, 3497, 3495, 3489, 3492, 
    3496, 3490, 3494, 6951, 3502, 3503, 
    3493, 3498, 3428, 12850, 12869, 12802
  )

Query time 0.00106

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "135.76"
    },
    "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": 39,
          "rows_produced_per_join": 39,
          "filtered": "100.00",
          "index_condition": "(`test2_gaseus`.`p`.`product_id` in (6843,6840,6841,6846,13274,13286,13280,13292,3430,3429,3437,3436,3438,3477,3452,3478,3479,3453,3491,3488,3497,3495,3489,3492,3496,3490,3494,6951,3502,3503,3493,3498,3428,12850,12869,12802))",
          "cost_info": {
            "read_cost": "22.66",
            "eval_cost": "3.90",
            "prefix_cost": "26.56",
            "data_read_per_join": "624"
          },
          "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": [
            "test2_gaseus.p.group_id"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 39,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "9.75",
            "eval_cost": "3.90",
            "prefix_cost": "40.21",
            "data_read_per_join": "15K"
          },
          "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": [
            "test2_gaseus.p.group_id"
          ],
          "rows_examined_per_scan": 7,
          "rows_produced_per_join": 273,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "68.25",
            "eval_cost": "27.30",
            "prefix_cost": "135.76",
            "data_read_per_join": "27K"
          },
          "used_columns": [
            "feature_id",
            "purpose",
            "group_id"
          ]
        }
      }
    ]
  }
}