SELECT 
  product_id, 
  feature_id, 
  variant_id 
FROM 
  cscart_product_features_values 
WHERE 
  product_id IN (
    45242, 45521, 45522, 45523, 45524, 45525
  ) 
  AND feature_id IN (24618) 
  AND lang_code = 'vi'

Query time 0.00583

JSON explain

{
  "query_block": {
    "select_id": 1,
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_product_features_values",
          "access_type": "range",
          "possible_keys": [
            "PRIMARY",
            "fl",
            "lang_code",
            "product_id",
            "fpl",
            "idx_product_feature_variant_id"
          ],
          "key": "PRIMARY",
          "key_length": "6",
          "used_key_parts": ["feature_id", "product_id"],
          "rows": 6,
          "filtered": 100,
          "attached_condition": "cscart_product_features_values.feature_id = 24618 and cscart_product_features_values.product_id in (45242,45521,45522,45523,45524,45525) and cscart_product_features_values.lang_code = 'vi'",
          "using_index": true
        }
      }
    ]
  }
}

Result

product_id feature_id variant_id
45242 24618 85917
45521 24618 85918
45522 24618 85919
45523 24618 85920
45524 24618 85921
45525 24618 85922