Architecture

Understanding the architecture of Trusted Server.

High-Level Overview

Trusted Server is built as a Rust-based edge computing application that runs on Fastly Compute platform.

Core Components

trusted-server-common

Core library containing shared functionality:

• Synthetic ID generation
• Cookie handling
• HTTP abstractions
• GDPR consent management
• Ad server integrations

trusted-server-fastly

Fastly-specific implementation:

• Main application entry point
• Fastly SDK integration
• Request/response handling
• KV store access

Design Patterns

RequestWrapper Trait

Abstracts HTTP request handling to support different backends:

// Placeholder example
pub trait RequestWrapper {
    fn get_header(&self, name: &str) -> Option<String>;
    fn get_cookie(&self, name: &str) -> Option<String>;
    // ...
}

Settings-Driven Configuration

External configuration via trusted-server.toml allows deployment-time customization without code changes.

Privacy-First Design

All tracking operations require explicit GDPR consent checks before execution.

Data Flow

1. Request Ingress - Request arrives at Fastly edge
2. Consent Validation - GDPR consent checked
3. ID Generation - Synthetic ID generated (if consented)
4. Ad Request - Backend ad server called
5. Response Processing - Creative processed and modified
6. Response Egress - Response sent to browser

Storage

Fastly KV Store

Used for:

• Counter storage
• Domain mappings
• Configuration cache
• Synthetic ID state

No User Data Persistence

User data is not persisted in storage - only processed in-flight at the edge.

Performance Characteristics

• Low Latency - Edge execution near users
• High Throughput - Parallel request processing
• Global Distribution - Fastly's global network
• Caching - Aggressive edge caching

Security

• HMAC-based IDs - Cryptographically secure identifiers
• No PII Storage - Privacy by design
• Request Signing - Optional request authentication
• Content Security - Creative scanning and modification

WebAssembly Target

Compiled to wasm32-wasip1 for Fastly Compute:

• Sandboxed execution
• Fast cold starts
• Efficient resource usage

Next Steps

• Learn about Configuration
• Set up Testing