API Building
Describe what an endpoint accepts, what it does and what it returns, and Arythmatic Flow serves it straight away at /h/your-api. There is no scaffolding to generate, nothing to deploy, and the auth, validation and rate limiting come with it.
Get Started FreeWhat You Get
Schema-validated payloads
Describe the accepted body as JSON Schema. Requests that do not match are rejected with 400 naming the exact fields that failed, before your logic runs.
Sandboxed processing logic
Write the handler in JavaScript with access to params, query, headers, body, the caller's identity and your stored secrets — and nothing else. No require, no fetch, no filesystem, with a hard timeout.
Auth and scopes
API keys, bearer JWT or basic auth per API, with per-endpoint scopes. A valid key without the right scope gets 403, not data.
Declared error responses
Define the errors your API can return, then select one from your handler by code. Anything unmapped becomes a 500 rather than leaking a stack trace.
Rate limiting
Per-API request ceilings by caller, returning 429 with Retry-After once exceeded.
Call logs
Every request recorded with status, duration and the failure reason, so a misbehaving integration is visible without extra tooling.
Frequently Asked Questions
Is this a replacement for a real backend?
For request-shaped work — validation, transformation, composing a response, gating access — yes. Handlers are pure transformation with no network or database reach, so anything that needs persistence or outbound calls still belongs in your own service.
How is it different from a mock server?
A mock returns a canned response. A hosted API validates the request against a schema, runs your logic and returns something computed, behind real authentication. Mock servers are still there for when a canned answer is all you need.
Where does it run?
On the same host as the rest of the platform, under a path namespace at /h/your-api — not a port per API, so it works behind one TLS terminator.
Can I test an endpoint before exposing it?
Yes. The editor runs your handler against sample input without publishing, and it uses the unsaved text so you can iterate before committing anything.