SELECT 
  product_id, 
  feature_short_desc 
FROM 
  cscart_ab__short_desc_from_features_values 
WHERE 
  product_id IN (276461) 
  AND lang_code = 'en' 
  AND storefront_id = 1

Query time 0.00046

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "0.85"
    },
    "table": {
      "table_name": "cscart_ab__short_desc_from_features_values",
      "access_type": "ref",
      "possible_keys": [
        "PRIMARY"
      ],
      "key": "PRIMARY",
      "used_key_parts": [
        "product_id",
        "lang_code"
      ],
      "key_length": "9",
      "ref": [
        "const",
        "const"
      ],
      "rows_examined_per_scan": 1,
      "rows_produced_per_join": 0,
      "filtered": "10.00",
      "cost_info": {
        "read_cost": "0.75",
        "eval_cost": "0.01",
        "prefix_cost": "0.85",
        "data_read_per_join": "3"
      },
      "used_columns": [
        "product_id",
        "feature_short_desc",
        "lang_code",
        "storefront_id"
      ],
      "attached_condition": "(`s2cart`.`cscart_ab__short_desc_from_features_values`.`storefront_id` = 1)"
    }
  }
}