SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3c584e701f545b9bd3b445cd80f63f1b39fd672909816422e83955168c111c63' 
  AND token = 'qbnf7JpjUUhOP2DjuRrAW0hCRNzoUxDnownQ3RCEQEU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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