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 (
    312419, 391002, 390979, 390978, 391013, 
    391014, 390986, 112217, 391009, 400923, 
    391023, 312417, 312421, 390994, 312426, 
    312427, 312428, 312429, 312430, 312431, 
    312432, 312433, 461018, 390974, 391026, 
    391008, 393787, 400916, 312423, 390980, 
    400921, 400925, 400922, 400924, 312420, 
    460961, 390977, 390984, 390981, 391005, 
    391003, 390987, 391006, 391004, 391007, 
    391028, 460952, 391015
  )

Query time 0.00046

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost": 0.03140489,
    "nested_loop": [
      {
        "table": {
          "table_name": "g",
          "access_type": "index",
          "possible_keys": ["PRIMARY"],
          "key": "idx_group_code",
          "key_length": "387",
          "used_key_parts": ["code"],
          "loops": 1,
          "rows": 2,
          "cost": 0.00693929,
          "filtered": 100,
          "using_index": true
        }
      },
      {
        "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": ["u985510652_ecartify.g.id"],
          "loops": 2,
          "rows": 1,
          "cost": 0.00527872,
          "filtered": 100
        }
      },
      {
        "table": {
          "table_name": "p",
          "access_type": "ref",
          "possible_keys": ["PRIMARY", "idx_group_id"],
          "key": "idx_group_id",
          "key_length": "3",
          "used_key_parts": ["group_id"],
          "ref": ["u985510652_ecartify.g.id"],
          "loops": 2,
          "rows": 8,
          "cost": 0.01918688,
          "filtered": 100,
          "index_condition": "p.product_id in (312419,391002,390979,390978,391013,391014,390986,112217,391009,400923,391023,312417,312421,390994,312426,312427,312428,312429,312430,312431,312432,312433,461018,390974,391026,391008,393787,400916,312423,390980,400921,400925,400922,400924,312420,460961,390977,390984,390981,391005,391003,390987,391006,391004,391007,391028,460952,391015)"
        }
      }
    ]
  }
}