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 (
    19799, 19678, 19546, 19811, 19545, 19809, 
    19810, 19815, 19814, 19812, 19813, 
    19558, 19673, 19557, 19850, 19851, 
    19847, 19846, 19845, 19848, 19849
  )

Query time 0.00073

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "f",
      "access_type": "ALL",
      "possible_keys": ["idx_group_id"],
      "rows": 6,
      "filtered": 100
    },
    "table": {
      "table_name": "g",
      "access_type": "eq_ref",
      "possible_keys": ["PRIMARY"],
      "key": "PRIMARY",
      "key_length": "3",
      "used_key_parts": ["id"],
      "ref": ["admin_test.f.group_id"],
      "rows": 1,
      "filtered": 100
    },
    "table": {
      "table_name": "p",
      "access_type": "ALL",
      "possible_keys": ["PRIMARY", "idx_group_id"],
      "rows": 15,
      "filtered": 80,
      "attached_condition": "p.group_id = f.group_id and p.product_id in (19799,19678,19546,19811,19545,19809,19810,19815,19814,19812,19813,19558,19673,19557,19850,19851,19847,19846,19845,19848,19849)"
    }
  }
}