Programming language: Crystal
License: MIT License
Tags: Examples And Funny Stuff    
Latest version: v0.7.0

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[Crystal World logo](media/logo.png)

Built with Crystal Build status Awesome vladfaust.com

Welcome to the Crystal World, a RealWorld back-end API application implemented in Crystal!


This project aims to demonstrate of how simple and enjoyable it is to develop a high-performance web application in Crystal, which is proven to be both fast and slick language, featuring:

  • โšก๏ธ Efficiency comparable to C
  • ๐Ÿƒ Beauty inherited from Ruby
  • ๐Ÿ”’ Type system with smart compiler

Crystal World relies on Onyx framework as its foundation. The database chosen is SQLite. Go ahead and read the source code, you'll find it delightfully simple and understandeable! ๐Ÿฐ

Note that although Crystal itself is not officially released yet, it's already being used in many real-world (including business) applications.


Clone this repository with

> git clone https://github.com/vladfaust/crystalworld.git && cd crystalworld

Crystal is a compiled language. It has different compilation modes, e.g. development and production. Production code is faster and packed into a single binary, however its builds take more time. Therefore, there are multiple ways to proceed:

Production build with Docker

  1. Build an image:
> docker build -t crystalworld:latest .
  1. Apply migrations:
> docker run -e DATABASE_URL="sqlite3://./crystalworld.db" crystalworld bin/cake db:migrate
  1. Launch the server
> docker run -p 5000:5000 -e DATABASE_URL="sqlite3://./crystalworld.db" \
-e JWT_SECRET_KEY="63a051d73d71c997d38946f82e708301" crystalworld

Production build from the source code

  1. Install Crystal on your machine
  2. Set env vars
> export DATABASE_URL="sqlite3://./crystalworld.db" CRYSTAL_ENV=production \
  1. Build the app
> time shards build --production --release --no-debug --progress --stats
  1. Apply migrations
> ./bin/cake db:migrate
  1. Launch the server
> ./bin/server

Development build from the source code

  1. Install Crystal on your machine
  2. Create an /.env.development.local file and put some environment variables there (see below)
  3. Apply migrations
> crystal src/bin/cake.cr -- db:migrate

or install Cake and exec cake db:migrate

  1. Launch the server in development mode
> crystal src/bin/server.cr --progress

Example output:

[Example terminal screenshot](media/terminal-screenshot.png)

Environment variables

Crystal World follows twelve-factor methodology and therefore relies on environment variables. You can see example and default variables at /.env.example file.


Crystal has a convenient testing environment built-in. Read more at Testing docs. Basically, you place specs under /spec folder and run them with crystal spec. It's also a good idea to have a separate /.env.test file.

Real World comes with integration testing suit, which can be found at https://github.com/gothinkster/realworld/tree/master/api. Crystal World uses this script in its CI, so if the badge is green it means that all the integration tests are passed. You can run these tests locally on your machine as well, just to be sure.



This software is licensed under [MIT License](LICENSE).

Open Source Initiative

*Note that all licence references and agreements mentioned in the crystalworld README section above are relevant to that project's source code only.