I run a small video downloader that pulls links from TikTok, Instagram, Facebook and YouTube. Every resolve starts with a call to a third-party API, and those APIs live on RapidAPI. When the site started getting real use, the free tier stopped being obviously enough — so before I spent a rupee on a paid plan, I sat down and did the maths.

What the free tier actually gives you

Most RapidAPI listings offer a free tier with a monthly request cap and a per-second rate limit. The numbers look generous until you translate them into what your site actually does. One visitor pasting one link is not one API call: my resolve endpoint tries the provider, and if the provider answers "Service is busy" it retries up to three times. A single bad afternoon can triple your usage without a single extra visitor.

So the first number I worked out was not the monthly cap. It was requests per successful download, averaged over a week of real traffic, retries included. That is the number the cap has to cover.

The maths that decides it

I kept it simple. Take the free tier's monthly allowance, divide it by the average requests per download, and you get the number of downloads the free tier supports. Then compare that with how many downloads you actually serve in a month. If the free tier covers you with room to spare, paying is just buying a bigger number you do not need yet.

The second part of the maths is the per-second limit. A burst of visitors at the same time can hit the rate limit even when the monthly total is fine. That was my real problem: not total volume, but the provider answering too fast for its own limit during a busy spell. A paid tier usually raises both limits, but if your problem is bursts rather than totals, a bit of queueing or a short backoff in your own code costs nothing and fixes the same thing.

What I actually ended up paying for

I did end up paying, but not for a bigger all-in-one plan. I bought two small dedicated services — one only for Facebook, one only for YouTube — because the single all-in-one provider kept going busy and its free tier was shared across every platform. Splitting platforms across providers meant one platform's bad day no longer took the whole site down, and each plan's cap was measured against one platform's real usage, not a blended guess.

That is the part people skip: a paid plan is not one decision, it is one decision per provider. I priced each platform separately, with its own request count, and only upgraded the ones that were actually hitting their cap.

The rules I now follow

  • Measure requests per download, not visitors. Retries and failed attempts count against the cap too.
  • Check the per-second limit, not just the monthly one. Bursts fail before totals do.
  • Price per platform. One busy provider should not force you to upgrade everything.
  • Stay on free until the numbers say otherwise. The day the maths flips is the day to subscribe, not before.
  • Keep a fallback. My resolve endpoint can say honestly that a provider is busy instead of pretending the link is broken. That one message has saved more goodwill than any paid tier.

I built the downloader at ramrom.io on this approach: free tiers first, real numbers second, paid plans only where a specific platform's usage proves it. The site costs very little to run, and the day it outgrows a free tier, the numbers will tell me — I will not have to guess.