This role is for one of the Weekday's clients

Min Experience: 6 years

Location: London

JobType: full-time

We are seeking a highly skilled Senior Software Engineer with deep expertise in Python and Large Language Models (LLMs) to join our growing engineering team. In this role, you will design, build, and scale intelligent systems that leverage modern AI capabilities to solve complex real-world problems. You will play a critical role in integrating LLMs into production environments, optimizing performance, and ensuring reliability at scale.

As a senior member of the team, you will be responsible for end-to-end development—from architecture design to deployment—while collaborating cross-functionally with product, data, and research teams. You should have a strong foundation in software engineering principles, along with hands-on experience building AI-driven applications using Python.

Requirements

Key Responsibilities:

• Design and develop scalable backend systems and APIs using Python.
• Build, fine-tune, and deploy applications powered by LLMs for use cases such as chatbots, content generation, summarization, and semantic search.
• Integrate third-party LLM APIs and/or open-source models into production systems.
• Optimize model performance, latency, and cost efficiency in real-time applications.
• Develop robust data pipelines for preprocessing, training, and inference workflows.
• Ensure high-quality code through testing, code reviews, and adherence to best practices.
• Collaborate with cross-functional teams to translate business requirements into technical solutions.
• Stay up to date with advancements in AI/ML, especially in the LLM ecosystem, and evaluate new tools and frameworks.
• Mentor junior engineers and contribute to technical leadership within the team.

Required Qualifications:

• 6–12 years of professional software engineering experience, with a strong focus on Python.
• Proven experience building and deploying production-grade systems.
• Hands-on experience working with LLMs (e.g., GPT-based models, open-source LLMs) and frameworks like LangChain, LlamaIndex, or similar.
• Strong understanding of RESTful APIs, microservices architecture, and distributed systems.
• Experience with cloud platforms such as AWS, GCP, or Azure.
• Familiarity with databases (SQL/NoSQL) and data processing pipelines.
• Solid understanding of software development best practices, including version control, CI/CD, and testing.

Preferred Qualifications:

• Experience with model fine-tuning, prompt engineering, and evaluation techniques.
• Knowledge of vector databases and embeddings (e.g., FAISS, Pinecone, Weaviate).
• Exposure to containerization and orchestration tools like Docker and Kubernetes.
• Background in machine learning or data science is a plus.