Senior Python Backend Engineer
First seen by Alion on Aug 28, 2026.
About the Role:
We are looking for a hands-on Senior Python Backend Engineer to build and scale an AI-driven sustainability platform. The role combines Python backend engineering, API development, data processing, and applied AI/LLM workflows.
You will work closely with engineering, product, QA, and domain experts to convert complex requirements into reliable, scalable, and production-ready solutions.
Key Responsibilities:
- Design, develop, and maintain scalable FastAPI/Python backend services and REST APIs.
- Build LLM/RAG-based applications, including prompt workflows, structured outputs, retrieval, grounding, and guardrails.
- Develop rule-based validations and workflows with proper traceability and auditability.
- Build reliable Celery-based background jobs with retries, monitoring, and failure recovery.
- Design data models and optimise PostgreSQL/SQL queries, caching, latency, and application performance.
- Write unit and integration tests using pytest and maintain high engineering standards.
- Contribute to Docker, Git, CI/CD, observability, security, and cloud deployments.
- Troubleshoot issues across applications, databases, distributed jobs, and third-party integrations.
- Collaborate with product, QA, engineering, and sustainability/LCA specialists to deliver features in Agile sprints.
Required Skills:
- 5+ years of professional software development experience with strong hands-on Python backend expertise.
- Strong production experience with FastAPI, Python, Pydantic, asynchronous programming, and service architecture.
- Good knowledge of REST APIs, authentication, validation, error handling, and API versioning.
- Strong experience with PostgreSQL/relational databases and SQLAlchemy or similar ORM.
- Hands-on experience with Celery and Redis/RabbitMQ or similar messaging systems.
- Experience developing LLM applications, RAG, embeddings, semantic search, structured outputs, or vector databases.
- Experience with pytest, Docker, Git, code reviews, CI/CD, and cloud-based applications.
- Strong debugging, analytical, and problem-solving skills.
- Good communication and ability to work with both technical and non-technical stakeholders.
- Interest in sustainability, climate technology, ESG, LCA, or carbon accounting is preferred.
Good to Have:
- Experience with LangChain, LlamaIndex, or similar LLM frameworks.
- Knowledge of LLM evaluation, hallucination control, retrieval quality, and human-in-the-loop workflows.
- Experience with vector databases, search/ranking systems, Pandas, NumPy, or data-processing workloads.
- Exposure to Sentry/monitoring, structured logging, microservices, Kubernetes, or infrastructure-as-code.
Skills
Backend Architecture, Python, FastAPI, Machine Learning, LLM, RDBMS