stats page serves 504 Gateway Time-out

### Problem

https://openlibrary.org/stats routinely serves 504 Gateway Time-out. After a few refreshes, the page usually loads properly.

### Reproducing the bug

1. Go to ...https://openlibrary.org/stats
2. Do ...

* Expected behavior: page loads
* Actual behavior: 504

### Context

- Browser (Chrome, Safari, Firefox, etc):
- OS (Windows, Mac, etc):
- Logged in (Y/N):
- Environment (prod, dev, local): prod

### Breakdown

#### Requirements Checklist
* [ ]

#### Related files

*

#### Stakeholders

*

#### Instructions for Contributors

- Please [run these commands](https://github.com/internetarchive/openlibrary/wiki/Git-Cheat-Sheet#working-on-your-branch) to ensure your repository is up to date **before** [creating a new branch](https://github.com/internetarchive/openlibrary/wiki/Git-Cheat-Sheet#making-changes-and-creating-a-pull-request) to work on this issue and **each time after** pushing code to Github, because the pre-commit bot may add commits to your PRs upstream.