SELECT 
  product_id, 
  feature_id, 
  variant_id 
FROM 
  cscart_product_features_values 
WHERE 
  product_id IN (
    11887, 11888, 11889, 11890, 11891, 11892, 
    11893, 11894, 11895, 11896, 11897, 
    11898, 11899, 11900, 11901, 11902, 
    11903, 11904, 11905, 11906, 11907, 
    11908
  ) 
  AND feature_id IN (553, 623) 
  AND lang_code = 'en'

Query time 0.00429

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "16.71"
    },
    "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": "idx_product_feature_variant_id",
      "used_key_parts": [
        "product_id",
        "feature_id",
        "lang_code"
      ],
      "key_length": "12",
      "rows_examined_per_scan": 72,
      "rows_produced_per_join": 72,
      "filtered": "100.00",
      "using_index": true,
      "cost_info": {
        "read_cost": "9.51",
        "eval_cost": "7.20",
        "prefix_cost": "16.71",
        "data_read_per_join": "55K"
      },
      "used_columns": [
        "feature_id",
        "product_id",
        "variant_id",
        "lang_code"
      ],
      "attached_condition": "((`gaseus`.`cscart_product_features_values`.`product_id` in (11887,11888,11889,11890,11891,11892,11893,11894,11895,11896,11897,11898,11899,11900,11901,11902,11903,11904,11905,11906,11907,11908)) and (`gaseus`.`cscart_product_features_values`.`feature_id` in (553,623)) and (`gaseus`.`cscart_product_features_values`.`lang_code` = 'en'))"
    }
  }
}