Using ISPConfig as Reverse Proxy with Docker for Hosting Multiple Joomla Sites (Best Practice?)

I’m currently working on a large-scale Joomla migration project at a university environment (around 500 websites), all currently managed through ISPConfig.

Our goal is to modernize the stack and standardize deployments, and I’m considering an architecture where:

• ISPConfig continues to handle:
  • Domain management
  • DNS
  • SSL (Let’s Encrypt)
  • Storage quotas
• While Docker is used to run the actual Joomla applications

The idea is to configure ISPConfig (Apache/Nginx) as a reverse proxy, forwarding requests to Docker containers running on localhost (different ports or via an internal router like Traefik).

Proposed flow:
Client → ISPConfig (SSL termination) → Reverse Proxy → Docker Container (Joomla)

Each site would:

• Keep its directory under /var/www/clients/... (managed by ISPConfig)
• Mount that directory into a Docker container
• Run Joomla isolated per container

Goals:

• Standardize Joomla environment across hundreds of sites
• Isolate applications (avoid one site affecting another)
• Simplify upgrades and maintenance
• Keep ISPConfig quotas and backups functional

Questions:

1. Has anyone implemented a similar setup with ISPConfig + Docker in production?
2. Are there any known pitfalls with using ISPConfig purely as a reverse proxy?
3. How well does this approach scale (hundreds of sites)?
4. Any concerns regarding permissions, quotas, or backups in this model?
5. Would you recommend introducing something like Traefik instead of managing ports manually?

I’d really appreciate feedback, especially from the ISPConfig team or anyone managing a large number of sites.

Thanks in advance!