Built‑in fetch vs custom native module: does concurrency increase latency in React Native?

Goal: determine if React Native's built‑in fetch API introduces higher latency when multiple requests are issued concurrently compared to a custom native networking module.

Constraints include platform‑specific connection limits per host, potential variations in JavaScript engine event‑loop behavior, and the fact that responses are handed to the JavaScript thread for sequential processing, which may serialize handling and affect perceived latency.

Key questions:

1. Does the built‑in fetch stack throttle concurrent connections and cause increased per‑request latency relative to a custom native module?
2. How does the nondeterministic order of promise resolution impact UI updates when many responses arrive simultaneously?
3. What measurable latency improvement can be achieved by offloading network handling to a native module on a separate thread?