SELECT 
  `link` 
FROM 
  cscart_custom_city 
WHERE 
  `link` = '?city_link=mytishchi'

Query time 0.00058

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "119.10"
    },
    "table": {
      "table_name": "cscart_custom_city",
      "access_type": "ALL",
      "rows_examined_per_scan": 1126,
      "rows_produced_per_join": 112,
      "filtered": "10.00",
      "cost_info": {
        "read_cost": "107.84",
        "eval_cost": "11.26",
        "prefix_cost": "119.10",
        "data_read_per_join": "597K"
      },
      "used_columns": [
        "link"
      ],
      "attached_condition": "(`dev2`.`cscart_custom_city`.`link` = '?city_link=mytishchi')"
    }
  }
}