transformer property
The default Transformer that transfers requests and responses into corresponding content to send. For response bodies greater than 50KB, a new Isolate will be spawned to decode the response body to JSON. Taken from https://github.com/flutter/flutter/blob/135454af32477f815a7525073027a3ff9eff1bfd/packages/flutter/lib/src/services/asset_bundle.dart#L87-L93 50 KB of data should take 2-3 ms to parse on a Moto G4, and about 400 μs on a Pixel 4.
Implementation
@override
Transformer transformer = FusedTransformer(
contentLengthIsolateThreshold: 50 * 1024,
);