Gleam - Type Safety That Doesn't Suck

Gleam is a programming language that tries to solve the "why did my production system crash at 2am?" problem. It's built for the BEAM virtual machine - the same runtime that keeps WhatsApp running with 2 billion users and Discord handling billions of messages.

Here's the problem: Erlang and Elixir don't give a fuck about typos until runtime. Write user.naem instead of user.name? Enjoy debugging that at 2am when your production system shits the bed.

Gleam fixes this by adding a type system that actually helps instead of getting in your way. It catches the dumb mistakes at compile time so you can focus on the interesting bugs. Released as v1.0 in March 2024, it's new enough that the ecosystem is still growing, but stable enough that companies are shipping it to production.

BEAM is Great, But Debugging Sucks

The BEAM VM is honestly incredible. It handles millions of concurrent connections without breaking a sweat, and when something goes wrong, it just lets it crash and restarts instead of taking down your entire system. WhatsApp achieved over 2 million connections per server using this architecture, and Discord uses it to handle chat for gamers who lose their shit when there's any lag.

The problem is debugging distributed systems when your language doesn't catch type errors until runtime. Ever tracked down a GenServer crash in production? It's like trying to debug someone's fever dream while your boss breathes down your neck asking when the API will be back up.

Gleam keeps all the good BEAM stuff - the Actor model, OTP supervision trees, hot code reloading, and the ability to run millions of processes - but adds a type system that catches the obvious mistakes before they become 3am production incidents.

import gleam/io

pub fn main() {
  // The compiler won't let you ship broken code
  io.println(\"hello, friend!\")
}

Shipping to Production (And It Actually Works)

Gleam v1.12.0 finally fixed dependency hell in August 2025. About fucking time - that should've been solved in v1.0. At least they promise not to break your code with updates, which beats the hell out of JavaScript's "oh btw we deprecated half the API" release notes.

What you get out of the box:

• Built-in toolchain: gleam new, gleam build, gleam test - everything works without configuration hell
• No build step bullshit: Run gleam new myapp and you have a working project, not a 500MB node_modules folder
• Access to all BEAM packages: Thousands of Erlang and Elixir libraries work (when the type boundaries don't bite you)
• Performance improvements: 30% faster JavaScript compilation in v1.11 because they actually give a shit about build times

The language has corporate backing from Lambda (not AWS Lambda, the consultancy), and they ship updates every 2-3 months. Each release actually improves things instead of adding seventeen new ways to configure your bundler.

Companies are already using it in production, which means you won't be the first person to find out that some feature breaks in weird ways when you scale it up.

Type Safety That Doesn't Make You Want to Quit Programming

Gleam's type system isn't trying to be fucking Haskell. Think "TypeScript but it doesn't lie to you." You get safety without needing a PhD to parse error messages. Come from JavaScript? The patterns look familiar. Come from Rust? Thank god you don't have to fight the borrow checker for basic shit.

No More Null Pointer Hell: Remember Cannot read property 'name' of null? Yeah, that doesn't happen in Gleam. Instead of null, you use Option types to represent "maybe there's a value, maybe there isn't":

import gleam/option.{type Option, None, Some}

pub fn find_user(id: Int) -> Option(User) {
  case users.get(id) {
    Ok(user) -> Some(user)
    Error(_) -> None
  }
}

Pattern Matching That Actually Helps: The compiler makes sure you handle all possible cases. Forget a case? It won't compile. This saves you from the classic "works on my machine" problem. Gleam v1.5 even shows you exactly which patterns you forgot, instead of making you guess.

Write Once, Run Everywhere (But Actually)

Here's the cool part: you write your code once, and it runs on both BEAM and JavaScript without any of that "some features don't work on platform X" bullshit.

BEAM Target: You get full access to OTP (Open Telecom Platform), which is basically a framework for building systems that don't fall over when things go wrong. GenServers, Supervisors, the whole distributed computing toolkit that keeps WhatsApp running.

JavaScript Target: Your Gleam code compiles to clean JavaScript that works in browsers, Node.js, Bun, whatever. The compiler even generates TypeScript definitions automatically, so you don't have to maintain two codebases or deal with "this might be undefined" in your integration layer.

// Same code works on both platforms
import gleam/list
import gleam/int

pub fn calculate_total(items: List(Int)) -> Int {
  list.fold(items, 0, int.add)
}

This isn't some "universal JavaScript" bullshit that breaks when you look at it wrong. Same language, same behavior, whether it's running in Phoenix LiveView or a React component.

Immutable Data That Doesn't Kill Performance

Everything in Gleam is immutable by default, which sounds like it would be slow as hell, but it's actually not. The runtime uses structural sharing behind the scenes, so when you "update" a record, it shares the unchanged parts instead of copying everything. Gleam v1.7 made this even faster.

pub type User {
  User(name: String, email: String, age: Int)
}

pub fn update_user_age(user: User, new_age: Int) -> User {
  // Creates new User with updated age, shares the rest
  User(..user, age: new_age)
}

This means you get all the benefits of immutability (no accidental mutations, easier testing, referential transparency) without the performance hit you'd expect from copying data structures all over the place.

Concurrency That Actually Scales

Gleam gives you BEAM's insane concurrency model with type safety on top. Remember Node.js with its precious single event loop that everyone pretends scales? BEAM laughs at that shit. You can spawn millions of processes and your system won't even flinch.

Lightweight Processes: Each process uses about 2KB of memory and runs in complete isolation. When one crashes, it doesn't take down anything else. It's like containers, but way lighter and faster.

import gleam/otp/process
import gleam/list

pub fn main() -> Nil {
  // Spawn 200,000 concurrent processes like it's nothing
  list.range(0, 200_000)
  |> list.each(spawn_greeter)
}

fn spawn_greeter(i: Int) {
  process.spawn(fn() {
    let n = int.to_string(i)
    io.println("Hello from " <> n)
  })
}

OTP Integration: Full access to OTP (Open Telecom Platform), which is the battle-tested framework that keeps telecom systems and messaging apps running. Gleam wraps GenServers, Supervisors, and other OTP behaviors with type safety, so you get all the reliability without the runtime surprises.

Developer Experience That Doesn't Suck

The Gleam Language Server works in VS Code, Vim, Emacs, basically any editor that supports LSP. You get code completion, jump-to-definition, real-time error checking - the stuff you expect to just work.

Error Messages That Actually Help: Instead of cryptic compiler errors, you get messages like this:

error: Unknown record field

  ┌─ ./src/app.gleam:8:16
  │
8 │ user.alias
  │     ^^^^^^ Did you mean `name`?

The value being accessed has this type:
    User

It has these fields:
    .name

The compiler actually tries to help instead of saying "fuck you, figure it out yourself" like most compilers.

Everything Works Out of the Box:

• gleam new myapp - Creates a working project with tests and everything
• gleam build - Compiles your code (no webpack config files)
• gleam test - Runs your tests (no jest.config.js)
• gleam format - Formats your code (no prettier arguments)
• gleam docs - Generates documentation that actually looks good

Performance: It's Fast Enough

Gleam v1.11 made JavaScript compilation 30% faster, and BEAM compilation keeps getting optimized. The language isn't as fast as C++ or Rust for CPU-intensive tasks, but for most web services and distributed systems, BEAM's performance characteristics are exactly what you want: predictable latency, graceful degradation under load, and the ability to handle millions of concurrent connections without falling over.

Building high-frequency trading? Use Rust or C++. Building web APIs, chat systems, or shit that needs to actually stay up? BEAM (and Gleam) handle that like champions.