rate limit
Like a turnstile that lets people through at a steady pace, it caps how many requests your app can make to a service in a given time.
Think of a counter that allows one person every few seconds. A rate limit sets a maximum number of requests, which are messages your app sends to a server, over a time window so the service stays healthy.
It matters because once you hit the cap, calls fail or slow down, which can break sign‑in, email, or data loads if you do not plan for it.
In practice you watch for errors like 429 Too Many Requests, which means you must slow down, then cache, which is saving a copy to reuse, back off, which is waiting longer before retrying, or batch, which is sending several items in one call.