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Erlang + Cowboy

Erlang + Cowboy for telecom-grade APIs.

BackendComplex

Stack Components

LanguageErlang 27
FrameworkCowboy 2
DBepgsql
DBPostgreSQL 16

Why

Fault-tolerant, hot reload, million connections. Node.js, Go, and Python are the top 3 backend languages (Stack Overflow 2024).

Go's goroutines handle 100k+ concurrent connections per process; Node's event loop excels at I/O-bound workloads.

When

Use for high-availability. Avoid for simple CRUD.

How

1. rebar3 new app app 2. Define handlers 3. Configure routes 4. rebar3 run 5. Add environment configuration — cp .env.example .env && edit values 6. Run tests — npm test or pnpm test to verify setup 7. Deploy — git push to trigger CI/CD or manual deploy

Example

init(Req, State) -> Req2 = cowboy_req:reply(200, #{}, users, Req), {ok, Req2, State}

Common Problems

  • ⚠OTP supervision — use supervisor for restarts
  • ⚠Hot reload — use sys:suspend/resume
  • ⚠Configuration drift between environments — use infrastructure-as-code (Terraform/Pulumi) to keep dev/staging/prod identical

Best Practices

  • ✓Use ranch for acceptors
  • ✓Leverage OTP for fault tolerance
  • ✓Set up health checks and graceful shutdown — handle SIGTERM to drain in-flight requests before exit

FAQ

What is Erlang + Cowboy and what projects is it for?

Erlang + Cowboy for telecom-grade APIs. It pairs layered technologies for end-to-end type safety and out-of-the-box deploys, fitting everything from MVPs to production SaaS.

How do I spin up a working demo with Erlang + Cowboy in 10 minutes?

Two steps: (1) rebar3 new app app; (2) Define handlers. Get the local dev server running, then wire one real data source to verify the end-to-end loop.

What is the most common pitfall with Erlang + Cowboy and how do I avoid it?

The most common pitfall is: OTP supervision — use supervisor for restarts. Avoid it by adding the matching checklist to your PR template and running type-check + lint + unit tests in CI — three gates before merge.

What are the best practices for Erlang + Cowboy?

Best practices for Erlang + Cowboy include: Use ranch for acceptors; Leverage OTP for fault tolerance; Set up health checks and graceful shutdown — handle SIGTERM to drain in-flight requests before exit. The first one — "Use ranch for acceptors" — should be set up at project init to avoid costly rework later.

When should I NOT choose Erlang + Cowboy?

Pick something else in three cases: (1) the team has zero experience with the core framework and the deadline is tight (learning-curve risk); (2) it's a pure content/marketing site (Astro is lighter); (3) you need very high throughput (>10k RPS) or strict-consistency microservices (Go/Rust). Erlang + Cowboy shines for mid-to-high complexity full-stack and API work — don't over-engineer simple static pages with it.