Trigger and scope

Trigger on: Fastly Compute, Compute@Edge, WASM on Fastly, fastlike, XQD ABI, Compute request lifecycle, 508 loop detection, backend subrequests, body streaming, embedding a Fastly Compute runtime in Go code, or any question about how Compute platform primitives work internally (caching, KV stores, edge rate limiting, ACLs, geolocation, secret stores, config stores, dictionaries, logging, dynamic backends, request collapsing, async I/O).

Do NOT use for: Fastly VCL (use falco), Fastly CLI/API (use fastly-cli or fastly), Viceroy, CDN comparison, WAF, Terraform, cache purging via API, or Fastly logging/stats configuration.

Fastlike — Local Compute Runtime & Reference

Fastlike is a Go implementation of the Fastly Compute ABI. It runs compiled WebAssembly programs locally, implementing the same 249+ host functions that Fastly's production Compute platform provides: backends, dictionaries, KV stores, caching, geolocation, rate limiting, ACLs, secret stores, and more.

Equally important, the fastlike source code is the most complete programmatic specification of how Fastly Compute works — its ABI implementations document every platform primitive, request lifecycle detail, and data structure as executable code.

Fastlike documentation: https://github.com/avidal/fastlike

Source Code as Compute Reference

When you have access to the fastlike source code locally (default: ~/src/fastlike), use these paths to answer specific Compute questions:

For a comprehensive guide, see understanding-compute-from-source.md.

Install from Source

Requires Go 1.23+.

# Clone and build
git clone https://github.com/avidal/fastlike.git ~/src/fastlike
cd ~/src/fastlike
make build        # Creates bin/fastlike

# Or install to GOPATH/bin
make install

# Or install directly
go install fastlike.dev/cmd/fastlike@latest

Quick Start

# Minimal: WASM + single backend
bin/fastlike -wasm app.wasm -backend localhost:8000

Fastlike vs Viceroy

When to use Fastlike: Non-Rust Compute apps, want custom geo data, need hot reload, debugging. When to use Viceroy: Rust Compute apps with cargo-nextest, Component Model projects, using fastly compute serve.

Common Configurations

With named backends:

bin/fastlike -wasm app.wasm \
  -backend api=api.example.com:8080 \
  -backend cache=redis:6379 \
  -backend localhost:8000

Development mode with hot-reload:

bin/fastlike -wasm app.wasm -backend localhost:8000 -reload -v 2

Send SIGHUP to reload the WASM without restarting.

Full configuration:

bin/fastlike -wasm app.wasm \
  -bind 0.0.0.0:5000 \
  -backend localhost:8000 \
  -dictionary config=./config.json \
  -kv store=./data.json \
  -config-store settings=./settings.json \
  -secret-store secrets=./secrets.json \
  -acl blocklist=./acl.json \
  -logger output=./logs.txt \
  -geo ./geodata.json \
  -compliance-region us-eu \
  -v 2 \
  -reload

Required Flags

Optional Flags

References