Architecture

mik-sdk uses a two-component architecture for WASI HTTP portability. This guide explains how the components work together.

Overview

Component Roles

Handler Component

Your handler contains:

Module	Implementation	Purpose
Business Logic	Your code	Request handling, validation, business rules
JSON	Pure Rust	Parsing and building JSON (no WASI calls)
Time	wasi:clocks/wall-clock	UTC timestamps, ISO 8601
Random	wasi:random/random	UUIDs, tokens, secure random
HTTP Client	wasi:http/outgoing-handler	Outbound requests (optional)

The handler exports the mik:core/handler interface.

Bridge Component

The bridge handles WASI HTTP translation:

• Imports mik:core/handler (your handler)
• Exports wasi:http/incoming-handler (standard WASI HTTP)
• Converts between WASI HTTP types and mik types
• Enforces body size limits (configurable via MIK_MAX_BODY_SIZE)

Composed Service

The two components are composed using WAC:

wac plug mik-bridge.wasm --plug handler.wasm -o service.wasm

The resulting component:

• Exports wasi:http/incoming-handler
• Can run on any WASI HTTP runtime
• Size: ~230KB (release build)

Interface Definition

The handler interface is defined in WIT:

package mik:core@0.1.0;

interface handler {
    enum method { get, post, put, patch, delete, head, options }

    record request-data {
        method: method,
        path: string,
        headers: list<tuple<string, string>>,
        body: option<list<u8>>,
    }

    record response {
        status: u16,
        headers: list<tuple<string, string>>,
        body: option<list<u8>>,
    }

    handle: func(req: request-data) -> response;
}

world handler-world {
    import wasi:clocks/wall-clock@0.2.0;
    import wasi:random/random@0.2.0;
    import wasi:cli/environment@0.2.0;
    import wasi:cli/stderr@0.2.0;

    export handler;
}

Request Flow

Build Process

Build Commands

# Build your handler
cargo component build --release

# Compose with bridge
wac plug mik-bridge.wasm \
    --plug target/wasm32-wasip2/release/my_handler.wasm \
    -o service.wasm

# Run
wasmtime serve -S cli=y service.wasm

Component Sizes

Component	Debug	Release
Handler (basic)	~500KB	~158KB
Handler (with http-client)	~700KB	~236KB
Bridge	~100KB	~72KB
Composed (basic)	~600KB	~230KB
Composed (http-client)	~800KB	~308KB

Optimization Tips

1. Use release builds: cargo component build --release

2. Enable LTO:

   [profile.release]
   lto = true

3. Disable unused features:

   mik-sdk = { version = "0.1", default-features = false }

WASI Imports

The handler component imports these WASI interfaces:

Interface	Purpose	Used By
wasi:clocks/wall-clock	Current time	time::now(), time::now_iso()
wasi:random/random	Secure random	random::uuid(), random::bytes()
wasi:cli/environment	Environment vars	env::get(), env::require()
wasi:cli/stderr	Logging output	log::info!(), log!()
wasi:http/outgoing-handler	HTTP client	fetch!().send() (optional)

Pure Rust Modules

These modules require no WASI calls:

Module	Description
json	JSON parsing and building
request	Request wrapper and parsing
typed	Derive macro implementations
query	SQL query builder

This design means JSON operations are fast and don’t cross the component boundary.

Portability

The composed component runs on any WASI HTTP runtime:

Runtime	Command
wasmtime	wasmtime serve -S cli=y service.wasm

Note

The -S cli=y flag enables stdio support for logging.

Security Boundaries

The WASM sandbox provides:

• Memory isolation: No access to host memory
• Capability-based security: Only granted WASI interfaces
• No filesystem access: By default (unless granted)
• Controlled networking: Only via wasi:http

Next Steps

• Installation - Set up your environment
• Quick Start - Build your first handler
• Routing - Learn the routing system