10000 users doesn’t mean anything. Are any of them going to visit the site?
Do you expect consistent traffic, or big surges when something happens? How many daily or monthy page views do you expect?
You should put assets on S3 as described at Configure an S3 compatible object storage provider for uploads and use CDNs.
If you’re on AWS or GCP or similar and have lots of money, then you should use managed DB.