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OCaml + Dream

Dream for OCaml web apps.

BackendComplex

Stack Components

LanguageOCaml 5.2
FrameworkDream 1
DBcaqti
DBPostgreSQL 16

Why

Type-safe, functional, async with Lwt. 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 OCaml web apps. Avoid for non-OCaml teams.

How

1. opam install dream 2. Define routes 3. run server 4. dune exec app 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

let () = Dream.run ~interface:'0.0.0.0' ~port:8080 @@ Dream.logger @@ Dream.router [ Dream.get '/users' (fun _ -> Dream.json users), ] // OCaml + Dream — usage example import { OCamlDream } from "ocaml-dream"; const result = await ocamldream({ input: "data" }); console.log(result);

Common Problems

  • ⚠Lwt async — use Lwt_unix for I/O
  • ⚠Templates — use Dream.syntax
  • ⚠Configuration drift between environments — use infrastructure-as-code (Terraform/Pulumi) to keep dev/staging/prod identical

Best Practices

  • ✓Use Dream.sql for DB
  • ✓Leverage OCaml's type system
  • ✓Set up health checks and graceful shutdown — handle SIGTERM to drain in-flight requests before exit

FAQ

What is OCaml + Dream and what projects is it for?

Dream for OCaml web apps. 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 OCaml + Dream in 10 minutes?

Two steps: (1) opam install dream; (2) Define routes. 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 OCaml + Dream and how do I avoid it?

The most common pitfall is: Lwt async — use Lwt_unix for I/O. 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 OCaml + Dream?

Best practices for OCaml + Dream include: Use Dream.sql for DB; Leverage OCaml's type system; Set up health checks and graceful shutdown — handle SIGTERM to drain in-flight requests before exit. The first one — "Use Dream.sql for DB" — should be set up at project init to avoid costly rework later.

When should I NOT choose OCaml + Dream?

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). OCaml + Dream shines for mid-to-high complexity full-stack and API work — don't over-engineer simple static pages with it.