mobin

A pastebin service built entirely in Mojo. Zero Python in the hot path: the HTTP server, WebSocket server, database layer, JSON serialisation, and routing are all Mojo code.

Live demo: mobin.fly.dev

• Backend: Mojo (flare HTTP + WS, sqlite, json, morph serde, uuid, tempo, envo, pprint)
• Frontend: Vanilla JS + nginx, live feed via WebSocket, auto-removal of expired pastes
• Infra: Docker Compose, single root pixi.toml (monorepo), GitHub Actions -> Fly.io CD

Architecture

graph TD
    subgraph Browser
        UI[HTML / JS frontend]
    end

    subgraph "Docker / Fly.io"
        direction TB
        NGINX[nginx :3000\nfrontend]

        subgraph Mojo backend process
            FORK[fork]
            HTTP[HttpServer :8080\nREST API]
            WS[WsServer :8081\nWebSocket feed]
        end

        SQLITE[(SQLite WAL\n/data/mobin.db)]
    end

    UI -->|HTTP GET /| NGINX
    UI -->|REST API calls| HTTP
    UI -->|ws://...:8081/feed| WS

    FORK -->|parent| HTTP
    FORK -->|child| WS

    HTTP -->|per-request connection| SQLITE
    WS -->|per-connection connection| SQLITE

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Quick start

pixi install          # resolve + install all Mojo dependencies
pixi run run-dev      # start backend on :8080 (HTTP) and :8081 (WS)

Open http://localhost:8080. The backend serves the embedded frontend directly.

Or with Docker Compose:

docker compose up --build
# Frontend: http://localhost:3000
# Backend:  http://localhost:8080

Documentation

Guide	What it covers
Architecture	Process model, database design, URL routing, stats table
API Reference	REST endpoints, WebSocket feed, TTL options, curl examples
Development	Repo layout, pixi commands, environment variables, integration tests
Package Management	Why Pixi, dependency pinning, dependency graph
Deployment	Fly.io, VPS + Docker Compose, Caddy TLS, Litestream backup
Performance	Local and live benchmarks
Security	Security checklist and resilience