Anyway, this whole thing confuses the hell out of me. You're receiving 3.6 billion requests per year and you've been serving it all for free with a single adsense ad and only making a couple grand a month off of it? I feel like I don't really understand. Shouldn't the hosting costs for multiple billions of requests be huge? Shouldn't you be charging for that? I'm speaking as someone who's never built anything like this, so I don't really know.
We do have paid accounts now but it doesn’t amount to a ton, around $440MRR.
I hesitated adding paid accounts for a long time because it cost so little to run but the ad revenue was alright.
Lots of niche markets out there, but my at revenue did take a long, slow path over 8 years to get to this point.
I found your project since you previously posted it on HN and linked to it in an answer below (hope you don't mind, I'll remove it if you want).
Pretty cool simple idea.
The API has been rewritten a few times now, it gets over 300 million requests a month. All organic growth, I can’t take any credit for it because I honestly have done nothing to aid it. Only use Google AdWords and it runs on a $40/m VPS.
We introduced paid plans a year ago and had a few sign ups. I think the paid accounts are about $440MRR but I split it with a friend who did all the work around paid accounts. (I didn’t think it would be worthwhile, he did, so he did the work around paid subscriptions)