Design and build scalable Python backends and APIs, integrate and deploy LLM-powered applications (chatbots, summarization, semantic search), optimize model performance and costs, develop data pipelines for training and inference, ensure code quality and CI/CD, collaborate cross-functionally, and mentor junior engineers.
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.
Similar Jobs
Cloud • Computer Vision • Information Technology • Sales • Security • Cybersecurity
Design, build, and operate highly scalable real-time streaming microservices and data pipelines (Java/Python/Go) using Kafka, Flink/Spark on Kubernetes across multi-cloud and on-prem. Own design, deployment, monitoring, observability, and on-call support while improving platform reliability and developer experience.
Top Skills:
Apache FlinkApache KafkaSparkApache StormAvroAWSCi/CdDatadogDistributed TracingGCPGitopsGoGrafanaJavaKubernetesOciParquetPrometheusProtobufPulsarPythonRabbitMQRestful ApisSplunk
Cloud • Computer Vision • Information Technology • Sales • Security • Cybersecurity
Design, architect, and develop scalable Go-based microservices and REST APIs for threat detection, case management, and incident response. Lead system design, own technical initiatives, mentor engineers, integrate AI/LLM capabilities, operate cloud-native services on Docker/Kubernetes and cloud platforms, participate in on-call rotation, and drive reliability and architectural improvements.
Top Skills:
Agentic Ai FrameworksAWSC#C++DockerGCPGoJavaKubernetesLlm IntegrationMicroservicesPythonRag PipelinesRestful ApisSIEMSoar
Fintech • Mobile • Payments • Software • Financial Services
Build and scale a price-comparison platform: implement robust scrapers, data ingestion and validation pipelines, and reliable backend APIs. Ensure data quality and observability, operate distributed event-driven systems, collaborate with product and data teams, own end-to-end delivery, and drive technical excellence through testing and reviews.
Top Skills:
AlertingAPIsData PipelinesEvent-Driven SystemsIntegration TestingJavaJvmKafkaKotlinLlmsMonitoringRelational DatabasesScraping TechnologiesSpringUnit TestingWeb Scraping
What you need to know about the London Tech Scene
London isn't just a hub for established businesses; it's also a nursery for innovation. Boasting one of the most recognized fintech ecosystems in Europe, attracting billions in investments each year, London's success has made it a go-to destination for startups looking to make their mark. Top U.K. companies like Hoptin, Moneybox and Marshmallow have already made the city their base — yet fintech is just the beginning. From healthtech to renewable energy to cybersecurity and beyond, the city's startups are breaking new ground across a range of industries.
