It’s fairly safe as long as you add a strong enough form of access control. For example if you put it behind a VPN, or a SSH tunnel, or require mTLS. Even a key in a custom HTTP header or Basic HTTP auth can be good enough if the key is strong enough.

You can further decrease the probability of drive-by bots reaching a publicly exposed service by merely scanning IPs and ports if you use a reverse proxy and hide your service FQDNs and IP.

You can do this by using TLS certs on wildcard domains rather than explicit domains, using explicit CNAMEs for the service subdomains rather than a wildcard domain, and keeping the A/AAAA records on an obfuscated subdomain rather than the base domain. If the bots can’t figure out a FQDN they’re not getting past the reverse proxy even if they find the IP and port.

This is obfuscation not real security but it cuts down tremendously on bot hits.