[BUG] Critical worker timeout in production
**Describe the bug**
In very rare cases, invoice is never marked as expired till the server restart

**To Reproduce**
Server must be running, invoice created, and then the gunicorn worker that created the invoice gets critical worker timeout and is restarted. This way invoice is lost

**Expected behavior**
Invoice not to expire

**Screenshots**
![изображение](https://user-images.githubusercontent.com/39452697/105217139-891a6e00-5b64-11eb-994e-2bf9e9c345c3.png)


**Desktop (please complete the following information):**
Version: latest

Opened a question at fastapi repo: https://github.com/tiangolo/fastapi/issues/2682