Polling is never not the best thing. For Google Sheets, I think it would be possible to build a proper Trigger-Node. For Airtable does it not seem like it though. When I looked I was not able to find anything to do that. So I guess polling it is.
If it does not execute to often (like if it would never overlap) and the data is not too large (like you said just an id) it would be possible to use static workflow data. With that, it is possible to save data with the workflow. Does, for example, get used for the Github-Trigger Node to save the webhook id. Looks like this:
const webhookData = this.getWorkflowStaticData('node');
webhookData.webhookId = responseData.id;
There are however two problems right now.
That method is not exposed in the Function-Node. That is, however, an easy fix and takes two minutes.
There seems to be a bug that the data does not get saved correctly when executing multiple times (like when triggered via Interval node or similar). No idea how much work that would be.
Normally I would try to fix it now asap but sadly things are still a little bit crazy from the launch and I am just answering emails, issues and community questions all day long. So do not know when I find time to look into that. Sorry!
An alternative would be to use the Postgres node to persist the value there. Or simply saving a file would also be possible.
I hope that helps!