Backend Game Logic Engineer

I’m building a persistent, browser based strategy MMO.
The UI is largely in place, I need an experienced backend engineer to implement the core game engine and logic, strictly following a written specification.

This is a logic heavy role, not a UI or design role.

What you’ll be responsible for
You will implement the backend systems that power the game, including:
- Colony state and ownership
- Resource production, storage caps, and protection
- Build / research / training / shipyard queues (time-based, server-authoritative)
- Fleet travel, ETA calculation, and recall windows
- Deterministic combat resolution (no RNG)
- Colonisation, conquest, and hard anti-griefing rules
- Technology effects on units, fleets, and travel
- APIs consumed by an existing frontend UI

The game is fully deterministic:
Given the same inputs, outcomes must always be identical.
- Non negotiable constraints

Please do not apply if any of these are a problem:
- No randomness in combat, travel, or production
- No “simplifying” mechanics
- No redesigning rules or systems
- No adding features that are not in the spec

This role is implementation, not interpretation.
What I’ll provide
- A detailed game design document defining all mechanics
- Clear formulas for combat, travel, sensors, queues, and tech
- An existing frontend UI to integrate against
- Fast feedback and decisions (no stakeholder mess)

Tech stack
- I’m flexible on stack, but you should be comfortable with:
- REST or equivalent API design
- Relational data modelling
- Time based systems (queues, timers, delayed resolution)
- Writing automated tests for deterministic logic

Please state:
- Your preferred backend stack
- How you would test deterministic systems
- Deliverables (initial milestone)

As a first milestone, I expect:
Backend logic + API for:
- Colony command screen (timers, resources, queues)
- Fleet launch, ETA calculation, recall logic
- Active missions list
- Basic automated tests validating core formulas
- Budget & engagement

Open to hourly or milestone based pricing
- Looking for quality over speed
- Long term work possible if this goes well

When applying, briefly describe:
- A system you’ve built where correctness mattered more than UX
- How you avoid logic drift over time