SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6a6f65340ab105510b9df09e76d2d1b2b75e30e9a2820883ab1428d23ff38c4c' 
  AND token = 'PzxGZATBnwJO66V/UbESTZg5TwPYqhg6JIy6g7EQjXs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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