SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '1256b09d365c423254c530592b58fdbd5eb180fb1e4a134bf57a9365fdb55dde' 
  AND token = '4zjyyfNXlNoUk2agoTxoShBmqgkndLcurycFqusPKUU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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