SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '90682b19c6f24df9a8f2d30cae1a916dd8e7db20870f2e64deb538da258b9032' 
  AND token = 'PxfHhtz0kGey4nUe5tCvOJXS5eRzxVlBwwVhYjVW+wI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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