SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b4998437a4ab98c0ce3c988ef8a38772f1981a5b49d01f61993fd435100b26b2' 
  AND token = 'FJDUlCE9pszDXHdQxmF8GK0y1xZ/iovsrZGYvz0uMZM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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