FFI Boundary Cost: Why Rust Isn't Always Faster in Flutter
Rust can make Flutter-adjacent compute much faster, but the native boundary is not free.
This benchmark compares a pure Dart data-processing lane against a direct `dart:ffi` Rust lane using the same seeded `Uint32List` workload, the same checksum path, two dataset sizes, and repeated measurement rounds.
Important scope note: this is not a `flutter_rust_bridge` package benchmark. It measures the lower-level direct FFI boundary underneath that broader architecture, so use the result as a baseline for boundary cost rather than a universal bridge-performance claim.
In this video:
Why Rust wins wall time and throughput in this workload
Where pure Dart still wins on peak RSS
Why copy cost and state flow matter for Flutter + Rust apps
How to decide when the FFI tax is worth paying
Verdict: move compute-heavy loops into Rust when the speedup clearly pays for the transfer. Keep work in Dart when memory density, simple state flow, and lower integration cost matter more.
#rust #flutter #dart #ffi #performance #benchmark #softwarearchitecture