Performance settings (concurrency vs. autoscaling)

The default behaviour is a deployment without autoscaling. However the concurrency settings haven't been set purposeful.

For example for the `stac` service we currently have:
```
WEB_CONCURRENCY: "5"
DB_MIN_CONN_SIZE: "1"
```

I would like to review or confirm the concurrency and autoscaling approach, eventually documenting it a bit more explicitly.