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FunQL Playground API: A public REST API for learning FunQL

The FunQL Playground API is now live — a hosted, no-setup environment for exploring FunQL, the Functional Query Language that simplifies and enhances how you query APIs.

Whether you want to try filtering, sorting, pagination, or just understand how FunQL behaves in practice, the Playground API offers a clean RESTful interface backed by real-world data and a complete OpenAPI Specification (OAS). The Playground API is fully open source on GitHub.

What is the FunQL Playground API?

The Playground API is the core of the FunQL Playground — an interactive, hosted environment where developers can learn FunQL by example. It lets you try FunQL queries directly, without installing anything locally or writing a single line of code.

Using standard REST endpoints, the API shows how FunQL's expressive query parameters work in practice — including advanced filtering, sorting on multiple fields, and robust pagination.

It is ideal for experimenting with FunQL in a live, realistic setting.

What can you do with it?

The Playground API currently exposes endpoints for three data sets:

  • Sets — A list of LEGO sets with metadata
  • Minifigures — Individual figures associated with sets
  • Designers — People who designed the sets

Each of these endpoints supports FunQL-style query parameters. The OpenAPI Specification (OAS) defines which fields support filtering or sorting and includes example values.

Here is an example of a FunQL query in action:

GET https://api.play.funql.io/v1beta1/sets?filter=
  and(
    eq(theme, "STAR_WARS"),
    gte(price, 500),
    gt(year(launchTime), 2010)
  )
  &sort=desc(price)

HTTP/1.1 200 OK
Content-Type: application/json

[
  {
    "id": "041a9eed-1665-40e5-876e-1875460cf730",
    "name": "LEGO Star Wars Millennium Falcon",
    "setNumber": 75192,
    "itemNumber": {
      "EUROPE": 6175770,
      "NORTH_AMERICA": 6175771
    },
    "pieces": 7541,
    "price": 849.99,
    "designerId": "ee6f6c30-f413-414f-a58c-ae3abf7776a3",
    "designer": {
      "id": "ee6f6c30-f413-414f-a58c-ae3abf7776a3",
      "name": "Hans Burkhard Schlömer"
    },
    "launchTime": "2017-10-01T00:00:00Z",
    "packagingType": "BOX",
    "theme": "STAR_WARS",
    "categories": [
      "VEHICLES",
      "ULTIMATE_COLLECTOR_SERIES",
      "MOVIES"
    ],
    "minifigures": [
      {
        "id": "146c0e19-7b76-4d23-8676-a5c38a0565d2",
        "name": "SW0878: Princess Leia (Hoth Outfit White)",
        "quantity": 1
      },
      ...
    ]
  }
]

Explore with Postman or your browser

You do not need to write any code to start experimenting.

What's in the GitHub repository?

The funql-playground-api repository contains everything needed to run, understand, and extend the Playground API:

OpenAPI Specification (OAS)

  • A structured, modular OpenAPI spec organized by paths, schemas, and parameters
  • Documentation of supported filters, sorting options, and pagination behavior

Database design

  • PostgreSQL schema defined in SQL files
  • Seed data for sets, minifigures, and designers in CSV format
  • Migration scripts for initializing the database

C# Application

  • Domain layer — Entity models based on the database
  • Infrastructure layer — Maps entities to PostgreSQL using Entity Framework Core
  • Application layer — Defines query models, request handlers, and response types
  • WebApi layer — Defines API endpoints and handles HTTP requests

Postman

  • A Postman Collection for exploring the API without writing any code

What's next?

This is the first in a series of blog posts about the FunQL Playground. Upcoming posts will explore:

  • How the OpenAPI Specification (OAS) is structured — and the conventions we follow
  • Using GitHub Actions and Redocly CLI to publish OpenAPI docs automatically
  • Using GitHub Actions and Docker to build the Web API and publish container images to Google Cloud Platform (GCP)
  • The upcoming FunQL Playground UI — a visual frontend for exploring queries

Stay tuned — and in the meantime, give the Playground API a spin!

Use the Postman Collection Explore the API docs