Node.js
The Node.js server type runs your bot with node. The Node version is chosen in Startup → Docker Image (Node 18, 20, 22 ... whichever your libraries need; discord.js v14 wants Node 18+). Change the image, restart.
Python
The Python server type runs python <PY_FILE>. Choose the Python version the same way via the Docker image. Packages are installed into a local prefix on every start, so a new image starts from a clean slate, and requirements.txt makes that painless.
Java
Order a Node.js or Python server and open a ticket: we switch it to a Java image and set the start command to your jar (java -jar bot.jar). JDA and Javacord bots run fine this way.
Other languages
Anything that runs on Linux can run here (Go, Rust binaries, Deno, Bun), and it works the same way as Java: ask us to set the start command. Tell us what the command would be on your PC.