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 (135, 139, 140, 141, 142, 143)

Query time 0.00020

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost": 0.033387764,
    "nested_loop": [
      {
        "table": {
          "table_name": "f",
          "access_type": "ALL",
          "possible_keys": ["idx_group_id"],
          "loops": 1,
          "rows": 4,
          "cost": 0.01066122,
          "filtered": 100
        }
      },
      {
        "table": {
          "table_name": "g",
          "access_type": "eq_ref",
          "possible_keys": ["PRIMARY"],
          "key": "PRIMARY",
          "key_length": "3",
          "used_key_parts": ["id"],
          "ref": ["cscart.f.group_id"],
          "loops": 4,
          "rows": 1,
          "cost": 0.007120904,
          "filtered": 100
        }
      },
      {
        "block-nl-join": {
          "table": {
            "table_name": "p",
            "access_type": "range",
            "possible_keys": ["PRIMARY", "idx_group_id"],
            "key": "PRIMARY",
            "key_length": "3",
            "used_key_parts": ["product_id"],
            "loops": 4,
            "rows": 6,
            "cost": 0.01560564,
            "filtered": 100,
            "index_condition": "p.product_id in (135,139,140,141,142,143)",
            "attached_condition": "p.product_id in (135,139,140,141,142,143)"
          },
          "buffer_type": "flat",
          "buffer_size": "5Kb",
          "join_type": "BNL",
          "attached_condition": "p.group_id = f.group_id"
        }
      }
    ]
  }
}