SELECT 
  * 
FROM 
  cscart_front_grid_data 
WHERE 
  category_id = 3 
ORDER BY 
  RAND() 
LIMIT 
  1

Query time 0.00252

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "5.15"
    },
    "ordering_operation": {
      "using_temporary_table": true,
      "using_filesort": true,
      "table": {
        "table_name": "cscart_front_grid_data",
        "access_type": "ALL",
        "rows_examined_per_scan": 49,
        "rows_produced_per_join": 4,
        "filtered": "10.00",
        "cost_info": {
          "read_cost": "4.66",
          "eval_cost": "0.49",
          "prefix_cost": "5.15",
          "data_read_per_join": "11K"
        },
        "used_columns": [
          "id",
          "category_id",
          "position",
          "cords",
          "image_url",
          "name",
          "company",
          "url",
          "params",
          "price",
          "pid"
        ],
        "attached_condition": "(`cscartdb`.`cscart_front_grid_data`.`category_id` = 3)"
      }
    }
  }
}