Please share your story - how did you start, what’s the product, what’s the magnitude of revenue.
I think the secret is building an api that on its own is a true niche offering. It would fit within an app that you can imagine others might build. That is key. A given feature of this mythical app, but be solved by the api. But solving a problem so complicated on its own, that someone would venture to not do it themselves, in a weekend.
Such is the case I suspect with SerpApi and Stripe, and the like. I've used a certain SQL layer, and considered crypto api layers before. Perhaps think about those domains?