Backend Game Developer (Node.js + MongoDB) — Server-Authoritative Mobile Game Offline

We are looking for an experienced Backend Game Developer to build the complete backend for Rogolos, a server-authoritative mobile game featuring combat, clans, card-based mechanics, economy systems, and seasonal progression.
The project includes a fully defined backend architecture and a complete module checklist — your job is to implement it cleanly, reliably, and production-ready.

This is an opportunity to build a full, real-time game backend from scratch using Node.js, Express, and MongoDB, following a clear, structured development plan.

⭐ What You Will Build

You will implement the full backend for Rogolos, including:

Core Systems

• Player profiles, authentication, equipment, inventories
• Tree system (levels, HP, production values, upgrades)
• Card mechanics, upgrades, effects, and usage
• Server-side combat with multi-round simulation
• Mana production, costs, real-time lazy regeneration
• Clans: creation, joining, tech levels, clan trees, donations
• Leaderboards and ranking updates
• Seasonal resets, rewards, and progression
• Economy systems (mana ↔ Rogolium exchange, premium offers)

Technical Architecture

• REST API built with Node.js + Express
• Event-driven gameplay flow (one event → one API action)
• MongoDB as the persistent state layer
• All game rules executed on the server (client = UI only)
• Modular repository-service-event architecture
• Full configs (GDD-as-code) separated from game logic
• Secure, scalable backend deployed on Hetzner

🔧 Responsibilities

• Implement all backend modules, routes, events, and services from the provided checklist
• Build clean, maintainable folder structure: /routes, /events, /services, /configs, /repositories, /models
• Create MongoDB schemas for players, trees, clans, cards, attacks, seasons
• Implement combat: damage, buffs, effects, multi-round logic
• Implement mana production via ManaService + ManaBatchUpdateEvent
• Add all gameplay endpoints (login, shop, combat, clans, inventory, economy, leaderboard)
• Write scalable services: CombatEngine, CardEffectEngine, BuffCalculator, EconomyService, RewardService
• Implement middleware: auth, validation, rate limiting
• Configure secure server environment on Hetzner (HTTPS, PM2, backups, firewall)
• Ensure code quality, logs, monitoring, and error handling across the backend

🧠 Required Skills

• Strong experience with Node.js and Express
• Deep understanding of MongoDB schemas, indexes, and aggregation
• Experience in building server-authoritative game backends
• Ability to implement complex game rules, buffs, combat systems, and economic logic
• Clear architectural thinking and ability to work with large modular systems
• Experience with authentication, validation, and security best practices
• Ability to write clean, modular, well-structured code

🎮 Preferred Experience

• Built backends for F2P mobile games
• Experience with combat simulations, card/buff engines, or turn-based logic
• Familiarity with GDD-as-code config patterns
• Strong understanding of real-time or asynchronous competitive gameplay
• Experience deploying and optimizing apps on Hetzner, AWS, or DigitalOcean
• Experience with logs, monitoring, alerting, and scaling strategies
• Ability to implement leaderboards and seasonal progression

📦 Tech Stack

• Node.js + Express
• MongoDB (server-authoritative state)
• REST over HTTPS
• PM2 or systemd
• Nginx or Caddy reverse proxy
• Git-based workflow
• JSON configs for all game rules
• Clean service/repository/event architecture

📅 Project Scope & Workflow

You will follow the full implementation checklist provided (step-by-step), covering:

1. Database layer & repositories
2. Player onboarding + mana system
3. Shop + cards + inventory
4. Combat engine + card effects
5. Clan systems
6. Leaderboards & seasons
7. Economy & premium offers
8. Final QA, load tests, and deployment setups

Milestones and roadmap are already defined.