Adding compute

What’s a Micro?

Deta Space can run almost any type of app. For example, Space supports:

  • frontend sites built with frameworks like React, Vue and Svelte
  • full-stack frameworks like Next, Nuxt or SvelteKit
  • backend apps built with Node.js, Python and even Go, Rust or something more custom.

A Space app can also be built by combining these different technologies, for example, a SvelteKit app with a Go API, really any combination of up to 5 different languages/frameworks.

We call these individual parts of an app Micros. A Micro is a lightweight compute service running inside your app which can be exposed to the outside using HTTP.

Micros are defined in your project’s Spacefile, telling Deta Space what Micros your app contains and how to run them.

Adding your first Micro

When you create a new project using the Space CLI, it will try to detect the type of app you want to deploy. This works for most frameworks like Next, Nuxt, SvelteKit, and backend runtimes like Node.js and Python.

If this detection works, it will show you what type of Micro is detected and its generated config. After you’ve confirmed the config is correct, the CLI will create the Spacefile in your local directory for you.

Even if this detection fails, Space supports almost any type of app via the Spacefile.

Adding Micros via the Spacefile

If you want to run something more custom or need to add more Micros to an existing project, you can edit the project’s Spacefile to add the required configuration.

Take a look at the Spacefile reference for a complete list of options.

Here’s the Spacefile for an app consisting of a single Node.js Micro:

v: 0
  - name: api
    src: ./node-api
    engine: nodejs16
    run: npm run start

The name field identifies your Micro inside your app and the src should point to the location of the Micro’s source code relative to your project’s root.

If your project contains more than one Micro, the primary field can be used to identify the entry point of your application (which Micro will be executed when the root path of your project is visited via HTTP).

Directory structure

A Micro can be thought of as its own independent service. As a result, they need to be self-contained in their own directory in your project and your project root should not contain any Micro specific files.

Here’s an example of the file & folder structure of an app with a Python backend and a Vue frontend:


All files needed for the Vue frontend (including package.json) are inside the frontend directory, while all files needed for the Python backend are inside backend.

Here is the matching Spacefile:

v: 0
  - name: frontend
    src: ./frontend
    engine: vue
    primary: true
  - name: backend
    src: ./backend
    engine: python3.9

🔑 It’s recommended to put your first Micro in its own sub-directory of your project. A single Micro will work running in the root directory of your project, but this approach doesn’t scale. You’ll have to migrate this Micro as soon as you want to add a second Micro to your project.

Micro Routing

Since your app can contain multiple Micros, the Space runtime needs to know what requests to route to which Micro.

On Space, this is handled by having a single primary Micro which receives all requests made to your app’s root path /. Each other Micro defined in your Spacefile will be served under a specific path relative to your app’s primary hostname. This is defined in the path field for each Micro in your Spacefile:

v: 0
  - name: client
    src: ./client
    engine: svelte
    primary: true
    path: client
  - name: api
    src: ./api
    engine: nodejs16
    path: api

In this example, the api Micro will be available at /api while all other paths including the root / will be received by the primary Micro, in this case, the static Micro client.

If the path is missing, the path will fall back to the name field.

Public Routes

If you want parts of your app to be available to the public (instead of being protected behind auth), you need to specify the routes with the public_routes keyword in your app’s Spacefile:

  - name: backend
    src: backend
    engine: python3.9
      - "/test" # exact match
      - "/public/*" # wildcards
      - "/api/*/docs" # wildcards can be placed anywhere

You can either match a route exactly, or use a wildcard (*) to match anything after it.

The paths specified with public_routes are relative to a given Micro’s root. This means you do not need to specify a Micro’s own path as part of its own public_routes. For example, if /api is served by a secondary (backend) Micro, and you want to make the route /api/public public, then you only need to specify /public as a public route for this Micro:

  - name: frontend
    src: frontend
    engine: static
    primary: true

  - name: backend
    src: backend
    path: api
    engine: python3.9
    - "/public" # This Micro is served under `/api` so if we want to make `/api/public` available to the outside we only need to specify `/public`

Requests made to your Micro matching any of the routes defined in public_routes will bypass Space’s authentication entirely.

Cross Micro Communication

Micros within a project are independent services, but can call one another to get what they need.

How you can successfully call one Micro from another one depends on if the calling Micro is sending the request from the browser or server side (from).

From the browser

If you are trying to call a backend Micro from another Micro in the browser, you can make requests to the relative path under which the Micro is served from:

// In the browser

That’s it. If Micros live in the same ‘project’, auth just works.

Server side

If you are trying to call another Micro from the backend you need to get your app’s assigned hostname to use as the origin, and use an api key to authenticate your request.

Both of these items are provided in the environment of the Micro:

  • The primary hostname is under the DETA_SPACE_APP_HOSTNAME environment variable.
  • The api key is under the DETA_API_KEY environment variable. This should be added as a header to your http request under X-API-Key.

Here’s how you’d make a request to a second Micro (on the path /second-micro) within an app, using Python:

import os

origin = f"https://{os.getenv('DETA_SPACE_APP_HOSTNAME')}"
api_key = os.getenv("DETA_API_KEY")
headers = {"x-api-key": api_key}

res = requests.get("/second-micro", headers=headers)

⚠️ If you expose this API Key, you risk compromising your Space app.

API Keys

If you want users of your app to be able to access their app instance programmatically you can enable the api_keys preset for Micros in your app:

  - name: api
    src: ./api/
    engine: python3.9
      api_keys: true

If enabled, users of your app will be able to generate API keys in their app instance settings and use them to authenticate requests made to otherwise private routes of a Micro.

Generated keys need to be provided in the HTTP header X-Space-App-Key and only work with Micros that have the preset api_keys enabled. Public routes have a higher preference than API keys, if there are public routes specified these will always be public.

Note: If you enable API keys you should show clearly in the app that API keys can be used and ideally have clear documentation on which endpoints of your app work with API key auth.

Micro Environment Variables

Pre-set Variables

The following environment variables will be set in all Micros, accessible on the server side.

  • DETA_PROJECT_KEY - deta project key
  • DETA_SPACE_APP - will be set to “true”
  • DETA_SPACE_APP_VERSION - the app version
  • DETA_SPACE_APP_HOSTNAME - will be set to the primary hostname
  • DETA_SPACE_APP_MICRO_NAME - micro’s name
  • DETA_SPACE_APP_MICRO_TYPE - will be set to "primary" if primary otherwise “normal”

Please let us know if you need additional configuration.

Custom Variables

Use the env preset if you need to set custom environment variables for your Micros. This can also be used to let users of your app specify things like external secrets or API Keys or Data Keys of different app instances.

  - name: api
    src: ./api/
    engine: python3.9
        - name: SECRET_MESSAGE
          description: Secret message only available to this Micro
          default: "deta is cool"
  • name : environment variable name or key
  • description : human friendly description (optional)
  • default : default value for the variable (optional)

The user of the app will be shown a UI in the App’s Settings where they can set the values for the specified environment variables. They will be exposed to the Micro’s environment under the specified name.

Custom Domains

If you already have your own domain you can assign it to any Builder or app instance with a few clicks. This “Custom Domain” works in addition to the default Space domain that gets assigned to an instance. The domain will be connected to the primary Micro of the app instance.

Follow just a few steps to add a custom domain to your app:

  • To add a custom domain to a Builder instance, open the Builder project and head over to the “Develop” page and then to the “Configuration” tab. Click “Add Domain” and enter your domain name.
  • To add a custom domain to an app instance you installed, open the app settings by clicking the 3 dots (…) next to the app’s icon on the Canvas, click “Settings” and then switch to the “Domains” tab. Click “Add Domain” and enter your domain name.

Before your domain is live, you need to setup a DNS record to point your domain to our servers. Follow the guide in our User Manual to learn how to do this.

Scheduled Actions

Scheduled actions allow an app to perform certain tasks on a specific interval. These tasks can be anything you build into your app, from a cleanup job to automated data aggregation or revalidation.

Adding a Scheduled Action

Scheduled actions are defined in the Spacefile on the Micro level:

  - name: backend
    src: backend
    engine: nodejs16
    run: "node index.js"
      - id: "cleanup"
        name: "Clean Up"
        description: "Cleans up unused data"
        trigger: "schedule"
        default_interval: "0/15 * * * *"

Each action with the trigger schedule needs to have a unique id, name, and default_interval at which it runs. You can optionally provide a description to inform the user about what the action is used for. More information on all the supported fields can be found in the Spacefile Reference.

When an action runs, a POST request containing the action id and the trigger in the event body will be sent to the Micro on the path /__space/v0/actions.

For example, the example Spacefile above will result in the following request body:

  "event": {
    "id": "cleanup",
    "trigger": "schedule"

It is up to you to handle the request and run whatever logic you need. You could for example call a function or interact with Base and Drive through the Deta SDK:

// using express'/__space/v0/actions', (req, res) => {
  const event = req.body.event

  if ( === "cleanup") {


Interval Types for Scheduled Actions

Space currently supports two types of intervals for scheduled actions:

Check out the Spacefile Reference on the exact syntax.

Scheduled actions have to be purposely enabled, setup and need to have a default interval which they will be executed on.

After installing an app, its scheduled actions are automatically enabled and set to run on the default interval. The user can at any point change the interval or disable an action completely. Check out the User Manual on how scheduled actions are presented to app users.