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Learn Fastly-compute-edge - 10 Code Examples & CST Typing Practice Test

Fastly Compute@Edge is a high-performance, serverless edge computing platform that allows developers to deploy code closer to users, enabling low-latency web experiences and fast content delivery.

View all 10 Fastly-compute-edge code examples →
Simple Fastly Compute@Edge Function (JavaScript)Fastly Edge Function with JSON ResponseFastly Edge Function with Query ParametersFastly Edge Function with POST BodyFastly Edge Function with HeadersFastly Edge Function RedirectFastly Edge Function Error HandlingFastly Edge Function Delayed ResponseFastly Edge Function Fetch External APIFastly Edge Function Conditional Response

Learn FASTLY-COMPUTE-EDGE with Real Code Examples

Updated Nov 25, 2025

Explain

Compute@Edge lets you run custom code at Fastly's edge locations globally.

Supports multiple languages and WebAssembly runtimes.

Optimizes content delivery by reducing latency and offloading work from origin servers.

Ideal for real-time personalization, security enforcement, and dynamic content generation.

Provides deep integration with Fastly's CDN and caching infrastructure.

Core Features

HTTP request/response handling at the edge

Custom logic execution in Wasm runtimes

Cache manipulation and content optimization

Routing, redirects, and header transformations

Logging and metrics collection for monitoring

Basic Concepts Overview

Edge Function - serverless code executed at edge nodes

Service - collection of edge functions and configurations

Version - versioned deployment of services

Cache - content stored at edge for fast delivery

Fastly VCL - domain-specific language for advanced routing and caching

Project Structure

src/ - source code for edge function

Cargo.toml / package.json - project dependencies

fastly.toml - Fastly service configuration

dist/ - compiled WebAssembly modules

scripts/ - build/deploy scripts

Building Workflow

Write function in supported language (Rust, AssemblyScript, C, etc.)

Compile to WebAssembly module

Configure service, routes, and triggers via Fastly CLI

Deploy module to global edge network

Monitor execution, logs, and cache performance

Difficulty Use Cases

Beginner: modify HTTP headers at the edge

Intermediate: cache API responses for faster delivery

Advanced: build edge-based personalization logic

Expert: implement multi-edge A/B testing and feature flags

Auditor: monitor edge performance and logging analytics

Comparisons

Compute@Edge vs Google Cloud Functions: runs at edge nodes, lower latency, CDN integrated

Compute@Edge vs AWS Lambda@Edge: similar edge serverless paradigm, Fastly emphasizes speed and developer ergonomics

Compute@Edge vs FunctionX: FX is blockchain smart contracts, Compute@Edge is serverless CDN-edge compute

Compute@Edge vs Cloudflare Workers: both edge compute, differences in platform, performance, and language support

Compute@Edge vs traditional serverless: edge deployed, globally distributed vs centralized cloud functions

Versioning Timeline

2019 - Initial release of Compute@Edge

2020 - Added WebAssembly runtime and Rust support

2021 - Expanded global edge locations and logging integrations

2022 - Improved developer CLI and local testing tools

2023-2025 - Expanded language support, performance optimizations, and advanced edge integrations

Glossary

Edge Function - serverless code executed at Fastly edge

Service - collection of functions and configurations

VCL - Fastly domain-specific language for routing/cache

Wasm - WebAssembly runtime for edge execution

Cache - content stored at edge for low-latency delivery

Installation Setup

Sign up for a Fastly account

Install Fastly CLI (`fastly`) locally

Create a Compute@Edge service project

Compile function to WebAssembly (Wasm)

Deploy function to Fastly edge via CLI or GitHub integration

Environment Setup

Install Fastly CLI

Create or select Fastly account

Configure API token for deployment

Install language toolchain (Rust/AssemblyScript/C)

Build and deploy first edge function

Config Files

fastly.toml - service configuration

Cargo.toml / package.json - dependencies

src/ - source code

dist/ - compiled WebAssembly module

scripts/ - build/deploy scripts

Cli Commands

fastly compute init -> initialize project

fastly compute build -> compile Wasm module

fastly compute deploy -> deploy service to edge

fastly compute serve -> run locally

fastly compute logs -> inspect execution logs

Internationalization

UTF-8 supported by default

Edge logic can apply localization per user/request

Global edge nodes reduce latency worldwide

Integration with translation APIs possible

Developers handle localized content in function code

Accessibility

Accessible globally via Fastly edge network

Controlled via API keys and ACLs

Edge logic applies to all HTTP requests

Supports CORS for web clients

Logs and metrics accessible via Fastly dashboard

Ui Styling

No native UI - backend only

Integrate with frontend apps via HTTP APIs

Custom responses can include HTML, JSON, or binary content

Use edge logic for A/B testing and personalization

Optional dashboards via Fastly UI

State Management

Stateless per request

Use external caches, databases, or APIs for persistent state

Temporary memory available during execution

Environment variables for configuration

No local storage persistence between requests

Data Management

Input via HTTP requests

Output via HTTP responses

Edge cache stores frequently requested content

Optional external database integration

Logs and metrics stored for monitoring

Architecture

Edge nodes distributed globally

Serverless runtime executing WebAssembly modules

Integration with Fastly CDN for caching and routing

Edge logic executed on HTTP request/response events

Observability via Fastly logging and metrics

Rendering Model

Client sends HTTP request -> edge node receives request

Edge function executes logic (modify headers, cache, personalize)

Cache or fetch from origin if needed

Send response back to client

Logs and metrics collected for monitoring

Architectural Patterns

Event-driven edge functions

Stateless execution per request

Integration with CDN caching and routing

WebAssembly-based runtime

Observability via logging and metrics

Real World Architectures

Personalized landing pages at edge

Edge-based security header injection

API response caching for high-traffic apps

A/B testing without origin load

Edge content transformation for images and JSON

Design Principles

Run code at the edge for ultra-low latency

Serverless and stateless by design

Integrate tightly with CDN caching and routing

High-performance WebAssembly runtimes

Automatic scaling and global distribution

Scalability Guide

Functions automatically run on all edge nodes

Stateless design allows unlimited concurrency

Optimize cache TTL for performance

Split heavy workloads into multiple functions

Monitor edge metrics to optimize latency and throughput

Migration Guide

Migrate CDN logic from origin to edge functions

Convert server-side code to WebAssembly-compatible runtime

Test function on staging service

Deploy globally at Fastly edge

Monitor logs, cache, and performance metrics

Performance Notes

Execution is near-instant due to global edge deployment

Reduces origin server latency and load

Optimized for short-lived, high-frequency requests

Memory and CPU constraints limit long-running computations

Global scaling is automatic and instant

Security Notes

Functions run in isolated WebAssembly sandbox

Use HTTPS for secure client communication

Validate all input and sanitize headers

Access control via Fastly service configurations

Monitor edge logs for anomalous activity

Monitoring Analytics

Use Fastly logging for request/response events

Monitor cache hit/miss ratios

Set alerts for edge errors or latency spikes

Analyze traffic patterns globally

Inspect edge metrics for performance tuning

Code Quality

Write idempotent edge functions

Optimize for memory and execution time

Test locally and with staging deployment

Use logging for debugging and observability

Monitor cache behavior and TTL efficiency

Practical Examples

Add custom security headers on all responses

Personalize homepage content per user location

Cache frequently requested API responses

Redirect traffic based on device or geography

Perform edge-based A/B testing for feature rollout

Troubleshooting

Verify WebAssembly compilation and compatibility

Check service configuration in Fastly dashboard

Inspect edge logs for request/response issues

Test cache invalidation and routing rules

Ensure proper memory and execution limits for edge function

Testing Guide

Use `fastly compute serve` for local testing

Deploy to staging version before production

Simulate HTTP requests with different headers

Check cache behavior and TTLs

Monitor logs for performance and errors

Deployment Options

Deploy via Fastly CLI

Use GitHub Actions for CI/CD deployments

Versioned deployments for rollback

Edge service configuration via dashboard

Gradual rollout using traffic splitting

Tools Ecosystem

Fastly CLI (`fastly`) for deployment

Fastly dashboard for configuration

Fastly API for automation

Local testing tools (`fastly compute serve`)

Observability: logging and metrics APIs

Integrations

Fastly CDN for caching and routing

Real-time logging and metrics

TLS and security headers

Custom VCL integrations for complex logic

Webhooks and external APIs for edge processing

Productivity Tips

Use Fastly CLI for rapid deployment

Test locally before edge deployment

Reuse WebAssembly modules for multiple services

Monitor metrics for performance bottlenecks

Automate deployments using CI/CD pipelines

Challenges

Debugging functions at edge nodes

Managing memory and execution limits

Complex cache invalidation rules

Monitoring global edge deployments

Integrating multiple edge functions for workflows

Learning Path

Learn WebAssembly basics

Understand edge computing and CDN concepts

Write and deploy a basic Compute@Edge function

Integrate caching and routing logic

Monitor performance and optimize edge delivery

Skill Improvement Plan

Week 1: WebAssembly basics and Rust/AssemblyScript

Week 2: Write simple HTTP transformations

Week 3: Add caching and personalization logic

Week 4: Integrate security headers and redirects

Week 5: Optimize performance, logging, and multi-edge routing

Interview Questions

What is Fastly Compute@Edge?

How does it differ from traditional serverless?

Explain how caching works with Compute@Edge

What are supported runtimes and languages?

How do you debug and monitor edge functions?

Cheat Sheet

fastly compute init - initialize project

fastly compute build - compile WebAssembly module

fastly compute deploy - deploy to edge

fastly compute serve - local testing

fastly compute logs - view edge logs

Books

Fastly Compute@Edge in Action

Serverless Edge Computing with Fastly

WebAssembly for Edge Applications

Edge Personalization and Optimization

High-Performance Web at the Edge

Tutorials

Getting started with Compute@Edge

Deploy your first edge function

Cache API responses at the edge

Implement security headers and redirects

A/B testing and personalization at edge

Official Docs

https://developer.fastly.com/learning/compute/

https://developer.fastly.com/reference/compute/

Community Links

Fastly Developer Hub

Fastly GitHub

StackOverflow Fastly tags

Fastly Community Slack

YouTube Fastly tutorials

Community Support

Fastly Developer Hub

Fastly GitHub repositories

StackOverflow Fastly tags

Fastly Community Slack

YouTube Fastly Compute@Edge tutorials

Monetization

Accelerate high-traffic websites and apps

Implement personalization and A/B testing

Enhance security and compliance via edge rules

Reduce origin server cost by caching at edge

Optimize API response delivery for SaaS products

Future Roadmap

Expanded language and runtime support

Enhanced debugging and local simulation tools

Improved observability and logging features

More advanced routing and cache orchestration

Better integration with third-party APIs and CDNs

When Not To Use

Long-running backend jobs

Applications requiring persistent storage

Heavy computational tasks exceeding Wasm limits

Projects outside web/CDN delivery context

Non-HTTP or non-CDN-driven workloads

Final Summary

Fastly Compute@Edge is a serverless edge computing platform.

Enables low-latency execution close to users via Fastly’s CDN.

Supports WebAssembly runtimes for multiple languages.

Ideal for personalization, caching, security, and dynamic content generation.

Globally distributed, scalable, and integrated with Fastly’s edge services.

Faq

Is Compute@Edge free?

Fastly offers free trial credits, then pay-per-use based on requests and bandwidth

What languages are supported?

Rust, AssemblyScript, C, and other WebAssembly-compatible languages

Does it scale automatically?

Yes - deployed globally at Fastly edge locations

Can I access a database from edge?

Yes, but latency may increase; best for caching or API aggregation

How long can a function run?

Execution limits depend on Fastly's Wasm runtime constraints, typically short-lived

Code Sample Descriptions

1

Simple Fastly Compute@Edge Function (JavaScript)

# fastly/demo/main.js
addEventListener('fetch', event => {
    event.respondWith(handleRequest(event.request))
})

async function handleRequest(request) {
    return new Response('Hello, Fastly!', { status: 200 })
}

A simple Fastly Compute@Edge function responding with 'Hello, Fastly!' to HTTP requests.

Let’s Try →
2

Fastly Edge Function with JSON Response

# fastly/demo/json.js
addEventListener('fetch', event => {
    event.respondWith(handleRequest(event.request))
})

async function handleRequest(request) {
    return new Response(JSON.stringify({ message: 'Hello, JSON!' }), {
        status: 200,
        headers: { 'Content-Type': 'application/json' }
    })
}

Returns a JSON response from a Fastly Edge function.

Let’s Try →
3

Fastly Edge Function with Query Parameters

# fastly/demo/query.js
addEventListener('fetch', event => {
    event.respondWith(handleRequest(event.request))
})

async function handleRequest(request) {
    const url = new URL(request.url);
    const name = url.searchParams.get('name') || 'Guest';
    return new Response(`Hello, ${name}!`, { status: 200 })
}

Reads query parameters and returns a personalized message.

Let’s Try →
4

Fastly Edge Function with POST Body

# fastly/demo/post.js
addEventListener('fetch', event => {
    event.respondWith(handleRequest(event.request))
})

async function handleRequest(request) {
    const data = await request.json().catch(() => ({}));
    return new Response(`Received: ${data.input || ''}`, { status: 200 })
}

Handles POST requests and parses JSON body.

Let’s Try →
5

Fastly Edge Function with Headers

# fastly/demo/headers.js
addEventListener('fetch', event => {
    event.respondWith(handleRequest(event.request))
})

async function handleRequest(request) {
    return new Response('Hello with headers', {
        status: 200,
        headers: { 'X-Custom-Header': 'FastlyEdge' }
    })
}

Returns a response with custom headers.

Let’s Try →
6

Fastly Edge Function Redirect

# fastly/demo/redirect.js
addEventListener('fetch', event => {
    event.respondWith(handleRequest(event.request))
})

async function handleRequest(request) {
    return Response.redirect('https://www.fastly.com', 302)
}

Redirects the request to another URL.

Let’s Try →
7

Fastly Edge Function Error Handling

# fastly/demo/error.js
addEventListener('fetch', event => {
    event.respondWith(handleRequest(event.request))
})

async function handleRequest(request) {
    try {
        throw new Error('Something went wrong')
    } catch(err) {
        return new Response(err.message, { status: 500 })
    }
}

Handles errors and returns a 500 response.

Let’s Try →
8

Fastly Edge Function Delayed Response

# fastly/demo/delay.js
addEventListener('fetch', event => {
    event.respondWith(handleRequest(event.request))
})

async function handleRequest(request) {
    await new Promise(resolve => setTimeout(resolve, 1000))
    return new Response('Delayed Hello!', { status: 200 })
}

Returns a response after a simulated delay.

Let’s Try →
9

Fastly Edge Function Fetch External API

# fastly/demo/fetch.js
addEventListener('fetch', event => {
    event.respondWith(handleRequest(event.request))
})

async function handleRequest(request) {
    const response = await fetch('https://api.github.com')
    const data = await response.json()
    return new Response(JSON.stringify(data), {
        status: 200,
        headers: { 'Content-Type': 'application/json' }
    })
}

Fetches data from an external API and returns it.

Let’s Try →
10

Fastly Edge Function Conditional Response

# fastly/demo/method.js
addEventListener('fetch', event => {
    event.respondWith(handleRequest(event.request))
})

async function handleRequest(request) {
    if(request.method === 'POST') {
        return new Response('POST received', { status: 200 })
    } else {
        return new Response('GET received', { status: 200 })
    }
}

Responds differently based on request method.

Let’s Try →

Frequently Asked Questions about Fastly-compute-edge

What is Fastly-compute-edge?

Fastly Compute@Edge is a high-performance, serverless edge computing platform that allows developers to deploy code closer to users, enabling low-latency web experiences and fast content delivery.

What are the primary use cases for Fastly-compute-edge?

Dynamic content generation at the edge. Real-time personalization for websites and apps. Security enforcement (e.g., bot mitigation, access control). A/B testing and feature flagging without hitting origin. API responses caching and optimization at edge nodes

What are the strengths of Fastly-compute-edge?

Ultra-low latency by running code at the edge. Reduces origin server load. High-performance, event-driven execution. Tight integration with Fastly CDN. Supports modern WebAssembly runtimes for multiple languages

What are the limitations of Fastly-compute-edge?

Stateless by design; no persistent storage. Limited execution duration and memory per request. Requires understanding of edge computing concepts. Debugging and local testing is less straightforward than cloud environments. Vendor lock-in due to Fastly-specific platform features

How can I practice Fastly-compute-edge typing speed?

CodeSpeedTest offers 10+ real Fastly-compute-edge code examples for typing practice. You can measure your WPM, track accuracy, and improve your coding speed with guided exercises.

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