SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5b28619c33b49357aae40077183d2aaa987ec011f4cb09d85bd8b36af81ad972' 
  AND token = 'baIrQrCYyx9oiD+34aWAHOk1EhmGkpIoLIlDIoVPUsU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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