Compiling n8n Workflow JSONs into Standalone Fastify/TypeScript Microservices (Open-Source + Client-Side Playground)

#n8n #typescript #node #opensource

n8n is fantastic for prototyping and visual orchestration. You can wire up webhooks, databases, and LLM calls in minutes.

The pain starts when a workflow grows into critical production infrastructure:

High-concurrency webhooks hit runtime overhead and container memory limits (~250MB+ per worker).
Subworkflows pay HTTP/DB round-trip overhead instead of running in-process.
Engineering workflows struggle with diffing 2,000-line JSON exports in Git, running unit tests, and enforcing strict TypeScript contracts.

To solve this without rewriting everything by hand, I built n8n-to-fastify — an Ahead-of-Time (AOT) compiler that converts exported n8n workflow JSONs into standalone Fastify + TypeScript microservices.

Try it live (100% client-side in your browser — zero data leaves your machine): rogeriomaciel.com.br/en/n8n-to-fastify
Source code (MIT): github.com/rogeriomaciel/n8n-to-fastify

How it works

Instead of interpreting JSON nodes dynamically at runtime, n8n-to-fastify parses the workflow DAG, resolves node dependencies and n8n expressions, and emits clean, idiomatic TypeScript modules (workflow.ts + routes/index.ts).

Currently supported nodes

Triggers & Responses: Webhook, Respond to Webhook
Flow & Logic: IF / Filter, Switch, Merge, Split Out, Aggregate, Wait
Data & Code: Set / Edit Fields, Code / Function
Integrations: HTTP Request, PostgreSQL, OpenAI / Gemini
Subworkflows: Execute Workflow compiled to an in-memory WorkflowRegistry (zero network round-trip between subworkflows)

Benchmark (Bun + Fastify)

On a compiled Lead Intake + Subworkflow validation pipeline (bun run benchmark):

Compilation time: 2.77 ms
Throughput: 1,885 req/s
Average latency: 0.530 ms
p95 latency: 0.742 ms

Honest Limitations

It does not cover all 400+ n8n community nodes yet. When the compiler encounters an unsupported node, it generates a typed TODO stub in the output TypeScript so you can drop in your own SDK or handler cleanly. Credentials are mapped to environment variables (process.env).

Try it & Break it

Paste any exported n8n workflow JSON into the in-browser playground or clone the CLI:

git clone https://github.com/rogeriomaciel/n8n-to-fastify
cd n8n-to-fastify
bun install
bun test

If a real-world workflow from your stack breaks on a specific node or expression ($json, $('Node'), etc.), open an issue on GitHub — and if you find the approach useful, a Star helps a lot!

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