Best Practices and Architecture Patterns

48.1 Architecture Patterns

Compute kernel JS/TS app + Wasm for a hot path (image filter, parser, compression). Keep the interface coarse-grained.

Library port Wrap an existing C/C++/Rust library with a clean JS API (TypeScript types, async loading) Full Wasm UI

Rust/C#/Kotlin/Dart framework rendering the UI (Leptos, Blazor, Compose, Flutter) Worker offload

Wasm runs in Web Workers. The main thread stays responsive (Comlink for RPC).

Plugin host An app embeds a runtime, defines a WIT/ABI, and runs third-party plugins with limits Edge function

Stateless request handlers as components (wasi:http) on edge/serverless platforms Polyglot composition

Components in different languages composed via WIT (shared-nothing linking) Sandboxed native dependency

Compile risky C libraries to Wasm, then to native (wasm2c / RLBox) for isolation

✅ Measure first: confirm Wasm actually beats optimized JS for your workload.

✅ Keep the JS↔Wasm interface coarse-grained. Pass buffers, not per-item calls.

✅ Use instantiateStreaming, serve application/wasm, compress with Brotli, cache aggressively.

✅ Optimize release builds (wasm-opt, LTO) and monitor binary size in CI (twiggy).

✅ Run heavy work in Web Workers. Use SIMD/threads with feature detection and fallbacks.

✅ Re-create typed array views after memory growth. Free allocated memory. Call .free()/.delete() on bound objects.

✅ Prefer memory-safe source languages (Rust) for security-sensitive code.

✅ Define interfaces with WIT for anything long-lived or polyglot. Version your plugin APIs.

✅ Grant minimal capabilities (WASI preopens, network access). Set fuel/memory limits for untrusted code.

✅ Ship debug symbols separately (DWARF/source maps) for production debugging.

✅ Test natively and in Wasm (browser and WASI). Fuzz parsers.

❌ Don't port DOM-heavy code to Wasm expecting speedups.

❌ Don't block the main thread with long synchronous Wasm calls.

❌ Don't trust guest-provided pointers/lengths in host functions.

❌ Don't rely on non-standard/experimental features in production without fallbacks.