Fetch API slow in [email protected] release build

Question

I use fetch in my react-native app for API calls. This works fine in development builds, but slows down to several seconds in a release build.

The problem is not with the API; a request takes about 100~300 ms to complete (according to the ngrok inspector). This is true for both dev and release builds.

When I log the time before and after the fetch, there's a delay that I can't explain.

The simplest use case (even in a fresh [email protected] app) slows down to a crawl when I do a API call in a release build.

console.log('start request');
const response = await fetch('http://...');
console.log('request completed');

The time between these logs varies between several 100ths of ms up to 6, 7 seconds (the non-async/await approach suffers the same sluggishness).

The response is always application/json, and I unpack it using the response.json() function. But even with a response such as {"test": 123}, it's still slow.

I can imagine having done something wrong during the react-native upgrade process, but what I don't understand is why this happens even in a completely boilerplate new react-native app.

All our tests indicate that iPods (6th gen) suffer this problem, not recent iPhones. Has anyone else encountered (and hopefully been able to fix) this?

Answer 1

Check with xmlhttprequest or use the axios instead of fetch api. And also check the time taken for this request in curl

In the terminal: curl -s -w 'Total: %{time_total}s\n' 'https://examplerequest.com'. So you can find what happen?