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 (
    312862, 312833, 312835, 312856, 312857, 
    312859, 312860, 312861, 312872, 312869, 
    312858, 312863
  )

Query time 0.00030

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": 70.58823395,
          "index_condition": "p.product_id in (312862,312833,312835,312856,312857,312859,312860,312861,312872,312869,312858,312863)"
        }
      }
    ]
  }
}