SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '68231841cb5652349d096bae40126e1fb08a48bf176d4d1939733f173bde6684' 
  AND token = '9ARPTYB0jfUfr5wmLwnPki7DI2tY7UQzXAlLo8XcoBY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00043

JSON explain

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