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 (
    534, 6559, 41229, 5500, 6554, 46716, 
    2458, 6555, 2255, 26854, 286, 6098, 
    25180, 5226, 405, 2414, 26864, 2797, 
    26846, 36834, 6367, 4460, 933, 1059, 
    6557, 1041, 2567, 25850, 6106, 3975, 
    1835, 2257
  )

Query time 0.00327

JSON explain

{
  "query_block": {
    "select_id": 1,
    "nested_loop": [
      {
        "table": {
          "table_name": "p",
          "access_type": "range",
          "possible_keys": ["PRIMARY", "idx_group_id"],
          "key": "PRIMARY",
          "key_length": "3",
          "used_key_parts": ["product_id"],
          "rows": 34,
          "filtered": 100,
          "index_condition": "p.product_id in (534,6559,41229,5500,6554,46716,2458,6555,2255,26854,286,6098,25180,5226,405,2414,26864,2797,26846,36834,6367,4460,933,1059,6557,1041,2567,25850,6106,3975,1835,2257)"
        }
      },
      {
        "table": {
          "table_name": "f",
          "access_type": "ref",
          "possible_keys": ["idx_group_id"],
          "key": "idx_group_id",
          "key_length": "3",
          "used_key_parts": ["group_id"],
          "ref": ["dev_db.p.group_id"],
          "rows": 1,
          "filtered": 100
        }
      },
      {
        "table": {
          "table_name": "g",
          "access_type": "eq_ref",
          "possible_keys": ["PRIMARY"],
          "key": "PRIMARY",
          "key_length": "3",
          "used_key_parts": ["id"],
          "ref": ["dev_db.p.group_id"],
          "rows": 1,
          "filtered": 100
        }
      }
    ]
  }
}