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 (
    38136, 38138, 38137, 387, 23152, 47921, 
    23267, 455, 5544, 4351, 4515, 2149, 
    48322, 734, 41339, 43817, 40437, 1896, 
    47632, 1893, 38074, 3288, 33310, 28159, 
    1894, 47631, 41345, 41341, 47597, 1767, 
    2139, 41340
  )

Query time 0.00545

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": 32,
          "filtered": 100,
          "index_condition": "p.product_id in (38136,38138,38137,387,23152,47921,23267,455,5544,4351,4515,2149,48322,734,41339,43817,40437,1896,47632,1893,38074,3288,33310,28159,1894,47631,41345,41341,47597,1767,2139,41340)"
        }
      },
      {
        "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
        }
      }
    ]
  }
}