Why do we have to make multiple calls? Can't we do a single call and then partition the data?

Multiple calls are often used to keep each request lightweight, improve cacheability, and reduce the risk of timeouts. A single call that returns a large payload can overwhelm the client, consume excessive bandwidth, and increase latency. Partitioning data after a single call also requires the client to download the entire dataset before filtering, which is inefficient. By breaking the data into smaller, logical chunks (e.g., pagination, filtering, or range queries), the server can send only what the client needs, enabling faster responses and better scalability. Additionally, multiple calls allow the server to apply different security or rate‑limiting rules per endpoint, and they make it easier to cache common subsets of data. Therefore, while a single call with client‑side partitioning is possible, it is usually less efficient and harder to maintain in production systems.