SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '50b41dd35f70815733cf277d3db16c7fdcbf291ec12d73666a79e9bd970eaace' 
  AND token = 'z9GylKfTBeBx1H+80l3ECVhuPT/wpt3wuOs+jBHqKQk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}