Are there any ways to give certain users with dynamic IP addresses access to a database behind a firewall?

Hi everyone,

I am a Postgres database developer and am currently working on a project for a client of mine. The database will have to sit behind a firewall, which will be setup by a third-party company.

Now there's the problem that I need certain web applications, which are hosted on AWS with dynamic IP-Addresses, to be able to connect to the database. There is no way to make these IP-Addresses static or even to determine a certain fixed range for them.

I don't know much about firewalls, but I assume that normal IP-Whitelisting will not work due to these circumstances.

My question is now: has anyone of you come across such a situation, and how would you solve this? Are there any other ways to authenticate access from dynamic IP addresses?

Any help is much appreciated! Thanks!