Senior Python/Django Backend Engineer – APIs, Domain Logic & Rules Engine

Project: Consumer Mobile Application Engagement: Freelance, hourly contract Duration: Initial 2 months, with potential for ongoing work Availability: 35-40 hours/week preferred, with regular overlap during Singapore business hours (GMT+8) Start: ASAP ABOUT THE PROJECT Friday.social is a new kind of social calendar that helps friends turn plans into real-life experiences. Our mobile application combines social planning, messaging and AI-powered assistance. We’re building on an existing Python/Django backend and currently consolidating our architecture, simplifying APIs and establishing consistent domain rules ahead of launch. We’re looking for an experienced Backend Engineer to accelerate development of core functionality, working alongside our existing engineer and an experienced Technical Advisor. This is a hands-on implementation role requiring strong systems thinking, independent engineering judgment and the ability to deliver production-quality code. SCOPE OF WORK - Backend development: Build and integrate Python/Django services, RESTful APIs and PostgreSQL database operations against defined product use cases. - Domain rules & rules engine: Implement complex business logic, permissions, state transitions and application workflows within an agreed architecture, including building and integrating rules-engine components as specifications are finalised. - Integration & data integrity: Ensure consistent behaviour across backend services and APIs, with appropriate validation, transactions, authentication and authorisation. - Engineering quality: Write maintainable code with automated tests, systematic debugging, error handling and regression coverage. - Technical collaboration: Work with our Technical Advisor on architectural direction, collaborate with our existing Backend Engineer and proactively identify technical risks or dependencies. TECH STACK Core: Python, Django, Django REST Framework, PostgreSQL Supporting: Redis, Celery, ASGI/WebSockets Infrastructure & Integrations: Render, AWS S3, n8n WHAT WE’RE LOOKING FOR - Strong hands-on Python/Django, Django REST Framework and PostgreSQL experience. - Proven experience building, shipping and maintaining production backend systems. - Strong experience implementing complex domain models, business rules, permissions and state transitions, with consistent rule enforcement across backend services and APIs. - Solid understanding of API design, database transactions, data integrity and asynchronous processing. - Excellent debugging, automated testing and software engineering practices. - Ability to work independently within an existing architecture, communicate clearly and take ownership of deliverables. Nice to have: Domain-driven design, rule engines, Redis/Celery, WebSockets, social networking or scheduling applications, and AI/LLM integrations. We value demonstrated engineering capability over years of experience. Ideally, you’ll have 5+ years of relevant backend experience and a track record of delivering reliable production software. EXPECTED DELIVERABLES The engagement will involve: - Developing and integrating assigned backend APIs and functionality against agreed specifications. - Implementing and testing canonical domain rules and rules-engine components. - Resolving integration issues and ensuring consistent backend behaviour. - Delivering automated tests and concise technical documentation to support ongoing maintenance. - Work packages will be prioritised progressively as product specifications are finalised. TO APPLY Please share: - Relevant experience: Examples of Python/Django backend systems you’ve personally built or maintained in production. - Technical problem-solving: Briefly describe a complex business logic, state management or backend architecture problem you’ve solved, including your approach. - Availability: Your hourly rate, weekly availability and ability to overlap with Singapore business hours. We’re looking for someone who can contribute quickly, exercise sound engineering judgment and take ownership of delivering reliable backend functionality