SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a537665796c6795be21e8d41544af753c3dd00dffe09e38549696dfbf97388a5' 
  AND token = 'oEhAAXWBaQ/CsH9vQ6MdR90jdN97TeHXXBYubc4lZnw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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