Is it possible to change limits and rules at runtime? Was there a UI for this?

The ability to change limits and rules at runtime depends on the architecture and implementation of the specific service. In some systems, especially those implemented in Go, dynamic configuration loading without restarting the application can be considered.

Typically, this is achieved through:

• Hot reloading of configuration — the application periodically reads configuration files or receives updates from a centralized storage (e.g., Consul, Etcd).
• Management API — a REST or gRPC interface is provided through which limits and rules can be changed on the fly.

Regarding the UI, mature systems often create administrative panels where operators can modify settings through a user-friendly interface, which then updates the service configuration.

As a general example, in Go, a watcher for a configuration file can be implemented:

func watchConfig(path string, updateChan chan<- Config) {
    watcher, _ := fsnotify.NewWatcher()
    defer watcher.Close()
    watcher.Add(path)
    for {
        select {
        case event := <-watcher.Events:
            if event.Op&fsnotify.Write == fsnotify.Write {
                cfg, err := loadConfig(path)
                if err == nil {
                    updateChan <- cfg
                }
            }
        }
    }
}

Thus, limits and rules can be changed without stopping the service if this is supported by the architecture. The presence of a UI depends on the project requirements and resources.