What's a rough estimate of signup traffic to expect for a free product?

I've launched on PH several times but it's been a while. 😁 My product is freemium, but I'm going to give away free lifetime licenses on launch day in the hopes it will spur more feedback from the community and learnings for me. And here's the thing... I'm bootstrapping the hell out of this. While I'm in this market validation phase I'm running the whole thing off of Replit and Airtable. I've got some pretty sick throttling and caching in place, but Airtable's API has a 5 requests/sec limit. So I'm trying to do some math and see how likely my throttler will be working overtime (and thus making my app seem slow). How many signups have you guys seen lately for decent-perfoming launches? Thanks!