Use a shared cache for gunicorn workers

[Kilo59]

References

1. https://realpython.com/python-memcache-efficient-caching/
2. https://stackoverflow.com/questions/43097811/how-can-i-share-a-cache-between-gunicorn-workers
3. https://krzysztofzuraw.com/blog/2017/gunicorn-lru-cache-pitfall.html
4. Set Caching Header issue Set a caching header by default #117