SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '20c971bf100d593fb6749ae628da31976fadb45b94876df9dd4511b97cc90266' 
  AND token = '4OJ8UFrMvST/YbYkqg3+LEOs2aslXFQfB8dAqELQu+M=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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