I have a Odoo Server (or take any JS server), deployed on AWS. Its POS works with JS, hence this subreddit.

I have connected an automated cashdrawer that works through the use of DLLs. Since I couldn't find anyway to connect, I used a third party (Firebase DB) to pass info to-and-fro between the device and the POS (I created a custom page to initiate the device and passed info to the real-time DB that the POS could fetch from).

Now, my query is that can I make this "real-time DB" an off-line server (I have a very unstable connection)?

I need the JS on AWS (Odoo server) to connect to localhost (the off-line DB, I've come across a similar name, rethinkDB) server from the web.
And since Odoo POS is capable of running off-line, I shouldn't face any issues.

I looked up on StackOverflow, they say we cannot (security issues).
If not, can you suggest any alternate solution.

P.S. The cloud server cannot even call the DLLs to communicate, or else, I wouldn't have used any 3rd party DB as a link.

Can you clarify the problem?

Either there is a need for offline work or the cash drawer needs integration (or a bast_rd workaround.)

For offline that's all up to the POS company.
For the cash drawer that is still up to them or if you are seeking a workaround my idea would be an app that looks for some event be it a file or a keyboard press to open the drawer. I take it you are a programmer just looking for ideas and not the end user.