Senior Backend Engineer at Xapien | London

Join Our Dynamic Team at XapienAt Xapien, we empower businesses to truly understand their connections with suppliers, investors, partners, and third parties. Our innovative approach merges speed, scale, and precision, utilizing advanced AI technology.Since our inception in 2018, we've evolved from a deep-tech startup to a key player in AI-driven due diligenc…

Join commercetools as a Senior Backend Engineer, where you will play a pivotal role in shaping innovative backend solutions using TypeScript. Collaborate with cross-functional teams to create scalable and resilient microservices that empower our clients to deliver exceptional digital commerce experiences.

Join Our Team as a Backend Software Engineer!Location: LondonAbout Us:We are a cutting-edge video platform designed for live, social, and mobile streaming. Our cloud-based solution simplifies the complexities of professional video production and distribution. We collaborate with leading broadcasters and rights holders such as Sky Sports, BT Sport, Eurosport, ITV, Turner, The Premier League, LaLiga, The FA, Buzzfeed, AELTC Wimbledon, GOAL.com, and more. Our platform seamlessly integrates with major social media channels including Facebook, Instagram, Periscope, Twitter, and YouTube, and we are proud to be a preferred global partner for Facebook Live.Utilizing Amazon Web Services as our primary hosting provider, we ensure that every product within our platform is architected for scalability and high availability, catering to a global clientele. Our cloud-based infrastructure empowers engineers to remain agile, providing them with the freedom to innovate without sacrificing reliability and development speed.We believe in cultivating talent by hiring bright graduate and junior engineers, integrating them into our dynamic culture, which is vital to our growth. From day one, you will be paired with a mentor who will guide you through daily technical queries and assist in your career progression, helping you to define your focus within our platform (video, data, front-end, architecture, streaming, etc.) through regular performance evaluations.Our commitment to your happiness and engagement is paramount. We encourage pushing our platform and team to leverage the latest technologies, providing you with a diverse set of responsibilities—from design and architecture to production support. This hands-on approach allows you to feel challenged and engaged, making a tangible impact.Our strategy has fostered an ideal environment for talent retention, with several of our senior engineers, including the current Product Owner and Lead Software Architect, having started as graduate engineers and evolved into key leaders within our organization.Being social is a core aspect of our culture. We enjoy bonding as a team and organize various activities to strengthen our camaraderie.If technology excites you, you’ll feel right at home with us!As a Backend Software Engineer, you will work on essential features of our flagship product, Studio. This may include developing automated clip creation services based on data analysis, improving our media transcoding services, or enhancing our live encoding platform.You'll be working with state-of-the-art technologies including Java, JavaScript, NoSQL, Serverless Architecture, Microservices, Auto Scaling/Auto Recovery, Kinesis, and Media Processing.

About UsAt Trainline, we are passionate about revolutionizing rail travel and creating a sustainable future for travelers. We empower millions to discover and book the best ticket options through our highly-rated mobile app, website, and B2B partner channels.Join Our Journey with Trainline As Europe’s leading rail app with over 135 million monthly visits and £6.3 billion in annual ticket sales, we partner with over 270 rail and coach companies across 40 countries. Our goal is to make travel simple, seamless, eco-friendly, and affordable.As a FTSE 250 company, we are proud of our diverse team of over 1,000 Trainliners from more than 50 nationalities, based in cities including London, Paris, Barcelona, Milan, Edinburgh, and Madrid. With plans for growth in the UK and Europe, now is the perfect time to join us on this fast-paced journey.Discover the Backend Teams at Trainline Our Backend teams are the backbone of Trainline’s exceptional product. We develop the journey search functionalities that millions rely on daily, build a secure eCommerce platform, and connect Trainline with over 270 travel operating companies in Europe and beyond. Each team focuses on specific domains, including journey search, fare calculations, bookings, payments, refunds, integrations, and real-time timetable information.As a Senior .NET Engineer at Trainline, You Will...Deliver innovative features using the most suitable tools and techniques.Prioritize quality in every aspect of your work.Continuously enhance the codebase to maximize efficiency.Keep our customers as the top priority in all developments.Identify and eliminate blockers and inefficiencies in processes.Make impactful contributions to technical decisions that shape our products.

Role Overview Utility Warehouse is looking for a Senior Backend Software Engineer to strengthen the Customer Lifecycle team in London. This role centers on building and refining backend systems that support every stage of the customer journey. The work has a direct impact on how customers experience Utility Warehouse services. What You Will Do Design, build, and maintain backend software that supports customer lifecycle processes Focus on efficiency and scalability to handle growing customer needs Contribute technical expertise to improve customer experience through reliable backend solutions About the Team Work alongside engineers who care about delivering quality service. The team values practical solutions and continuous improvement, with each member playing a key role in shaping the technology that powers Utility Warehouse’s customer interactions.

About the RoleWe are seeking a skilled Senior Backend Engineer to tackle some of the most challenging issues in cybersecurity. In this role, you will help build a cutting-edge platform that integrates over 150 security tools, supports enterprise clients at scale, and drives innovative AI capabilities. Working primarily with C#/.NET on AWS, you will collaborate closely with the Head of Engineering and a passionate team dedicated to excellence in their work. If you are an outstanding engineer eager to create meaningful impact, this opportunity is for you.Why Choose ThreatAware?At ThreatAware, we empower security teams by providing a comprehensive source of truth for all devices and tools within their organizations. With over 150 integrations and deployment in under 30 minutes, our platform offers real-time visibility across entire IT estates. Clients in finance, legal, energy, and healthcare trust us to safeguard their assets.We are now embarking on an ambitious project to enhance our existing six years of accurate cyber asset data by integrating AI capabilities. This will enable security teams to analyze their data, automate workflows, and proactively manage risks before they escalate. The platform you will contribute to is fundamental to this vision.Your ResponsibilitiesAs a Senior Backend Engineer, you will:Contribute to the design and evolution of our core architecture, including the integration framework, APIs, data models, and scalable multi-tenant infrastructure.Develop backend services that support our AI features, creating APIs and data pipelines that provide real-time asset data to large language models.Enhance our integration platform connecting over 150 security tools by designing streamlined, reliable, and efficient integration patterns.Address complex engineering challenges such as event correlation, high-throughput data pipelines, and the development of secure, high-performance APIs.Mentor fellow engineers through code reviews, design discussions, and architectural strategies to elevate the team's overall quality.QualificationsProven expertise in C#/.NET development, with strong instincts in system design that uplift your colleagues.Experience with multi-tenant SaaS platforms on AWS or similar cloud infrastructures.Solid skills in API design and database architecture, always considering scalability, reliability, and maintainability.A keen interest in AI and LLMs, driven by a passion for developing backend solutions that leverage these technologies.A collaborative mindset with a commitment to team success.

Join Us in Empowering the UK’s Small Businesses! Small enterprises are the cornerstone of our economy, and at Funding Circle, we are dedicated to ensuring their success. Our innovative platform harnesses advanced data analytics to provide rapid funding solutions—transforming the traditional process of weeks into mere minutes.Funding Circle embodies the dynamic spirit of a fintech start-up combined with the stability of a publicly traded company. This unique environment empowers our team members, affectionately known as Circlers, to take initiative and create meaningful change.We pride ourselves on being a high-performing team that uplifts one another. We challenge, support, and collaborate, understanding that together we can achieve greater results.Our impact is significant: In the past year, the businesses utilizing our platform generated £7.2bn for the UK economy Be part of a mission that truly matters![Explore our Impact Report] | [Check our Trustpilot reviews]Your Role London (Hybrid) | 2 days in the office | Competitive Salary + BenefitsWe are seeking a Senior Backend Engineer to join our Customer Authentication team. In this role, you will contribute to developing the essential security and identity platforms that facilitate Funding Circle's shift towards a modern, distributed architecture. You will oversee critical systems that ensure secure customer access and manage complex business relationships across all product teams.Design, build, and maintain authentication and authorization systems.Translate product requirements into technical solutions and deliver them effectively.Collaborate closely with Product Management and other engineering teams utilizing your systems.Passionate about developing new solutions—much of our team's work involves greenfield projects—while also willing to engage with existing codebases.Thrives in a complex problem domain, implementing straightforward software systems.A team player who values collaboration and knowledge sharing over isolated work.A mentor at heart, generously sharing your time and expertise to advance the skills of stakeholders and fellow engineers.

About Us:Omaze is dedicated to transforming lives through charitable giving. By offering our community in the UK and Germany the opportunity to win luxurious homes and transformative prizes, we simultaneously raise much-needed funds for beloved causes.In just five years, our incredible Omaze Community has helped generate over £100 million for charities across the UK, supporting vital organizations such as Age UK, the RSPCA, the British Heart Foundation, and Great Ormond Street Hospital Charity.And this is just the beginning. At Omaze, we are cultivating a culture focused on growth and making a substantial global social impact.Why You'll Love Being Part of Omaze:Growth: Join one of the fastest-expanding companies worldwide.Impact: Collaborate with passionate individuals dedicated to making a positive difference.Innovation: Contribute to a groundbreaking mission that has never been attempted before.Culture: Experience a workplace where hard work, collective growth, and joy are celebrated. Role OverviewAs a Senior Backend Engineer at Omaze, you will leverage your expertise to develop cutting-edge social good platforms that enable nonprofits to amplify their impact. Your commitment to high-quality code and your ability to balance technical craftsmanship with customer value are paramount. You should showcase a diverse knowledge of technologies and their application in designing features or systems.Effective communication and organizational skills are critical as you will translate concepts and requirements into actionable deliverables. Collaborating with both technical and non-technical teams will be a regular part of your role, and you will continually aim to enhance your skills and those of your colleagues. Your belief in the value of diversity and inclusion will be central to your mentorship approach, fostering growth in others.This position allows you to take ownership of the technical quality, execution, and delivery of user stories. Key ResponsibilitiesUtilize your engineering expertise to collaborate with a dynamic engineering team in creating impactful social good platforms.Write and test code and infrastructure essential for application development.

Why Choose Verifone?With over 40 years of excellence in the electronic payment technology sector, Verifone has emerged as a leader in providing innovative payment solutions globally. We proudly collaborate with top retailers, banks, and partners to enhance payment processing systems worldwide.Our work environment is diverse, dynamic, and fast-paced, offering employees ample opportunities for professional growth. At Verifone, we strive for excellence in our products and services, focusing relentlessly on customer satisfaction. Join us in our commitment to innovation, as we pave the way for secure payment solutions across various markets.We believe in the power of collaboration and are currently offering a hybrid work schedule while continually assessing our attendance policy to optimize employee engagement.Role OverviewWe are looking for aSenior Software Developer in London to design, develop, and maintain backend services for our global payment gateway. Your expertise will contribute to building high-performance, secure microservices using Java and Spring Boot. You will collaborate with various teams to ensure our systems scale reliably across regions and partners.This role plays a crucial part in enhancing the reliability, security, and performance of high-volume financial transactions worldwide, making your engineering decisions vital to our success.Ideal candidates are senior backend developers passionate about complex distributed systems, modern Java platforms, and cloud-native architectures.

Do you have the passion to drive innovation? Join AnyVan and revolutionize the way we move anything, anywhere while building a fulfilling career that accelerates with every challenge. Founded in 2009 by our visionary CEO Angus, AnyVan emerged from the need to optimize logistics by utilizing underused van space. Our mission is to transform logistics technology, dramatically reducing wasted journeys and carbon emissions. With over 150,000 five-star reviews and a customer base exceeding 5 million across the UK and Europe, we are proud to be the preferred choice for countless users. Our dedicated team of 400 AnyVanners, operating from London, Cape Town, and Bogota, is committed to reducing carbon emissions by 8,520 tonnes annually. Be at the forefront of logistics innovationAt the core of our operations is a cutting-edge optimization platform that seamlessly connects customer needs with real-time driver availability, enabling us to provide exceptional service at unbeatable rates.By efficiently matching jobs with drivers already on the road, we minimize unnecessary miles, reduce emissions, and ensure fair earnings for our drivers. It’s a complex interplay of logistics, pricing, and marketplace dynamics, all powered by advanced software.And this is just the beginning...As we embark on the next phase of development, we're transitioning our platform to a truly intelligent logistics marketplace. Your role will involve designing and building systems to:Accurately model job-level costs in real time, paving the way for smarter, more dynamic pricing strategies.Enhance our driver platform, integrating it deeper into their daily operations and unlocking new revenue streams.Establish a two-sided marketplace, facilitating the buying and selling of non-core jobs among drivers to optimize utilization.Scale efficiently as we grow in volume, complexity, and ambition.This position is ideal for engineers who thrive on tackling complex, high-impact challenges and shaping the evolution of a scalable platform.

Join Superis Labs in our mission to create a high-performance perpetual futures decentralized exchange (DEX) built on the Solana blockchain. As we develop our first production MVP, you will play a critical role in shaping the core architecture and protocol design of our innovative platform.Superis Labs is proudly supported by Ergonia, a leading market-making firm and venture builder with extensive expertise in trading and development on the Solana network. In this dynamic environment, we are rapidly iterating from a minimal core towards a fully-featured mainnet exchange. This position offers significant ownership and the opportunity to build production systems under tight deadlines.Key Responsibilities:Develop core exchange functionalities including markets, user management, collateral handling, fee structures, and order routing.Implement robust liquidity sources, on-chain matching, margining, liquidation, and risk enforcement mechanisms.Contribute to the design of the comprehensive architecture for the perpetuals exchange.Ensure seamless operation of on-chain and off-chain systems as a unified, low-latency stack.Optimize systems for performance, latency, and computational efficiency.Create thorough testing protocols and maintain clear, up-to-date documentation.Enhance developer tools and improve onboarding processes.Design, implement, and deploy production-level Solana smart contracts using Rust.

Join xAI as a Backend Engineer, where you will play a vital role in building robust production systems that support grok.com and our API. We are looking for a highly motivated individual with expertise in scalable infrastructure and a passion for problem-solving. Your experience with Rust or C++, along with your ability to design and maintain distributed systems, will be crucial as you contribute directly to our mission of advancing AI technologies. Strong communication skills and a commitment to excellence are essential in our collaborative environment.

At Octopus Energy, we began with an audacious vision: to establish the UK's first fully digital energy supplier. Our journey has been driven by cutting-edge technology and a passionate team dedicated to customer satisfaction and the green energy transition. In 2025, we proudly became Britain's largest energy supplier.Today, we are rapidly expanding, developing innovative products that facilitate the transition to renewable energy. From simplifying the switch to heat pumps and solar energy to launching intelligent tariffs and scaling renewable energy generation, we tackle the most intricate challenges in the energy sector with agility, creativity, and a strong focus on customer needs. Our mission extends globally as we empower our international operations to share the successful innovations and experiences we've cultivated in the UK.Joining our Tech team means you’ll have the autonomy, diversity, and opportunity to design products that significantly impact individuals' lives—reducing energy costs, promoting sustainable living, and delivering exceptional customer experiences. You'll collaborate closely with teams from marketing, operations, and data, witnessing the real-world effects of your contributions.We invite you to apply for the position of Senior Backend Engineer within our Flexibility team.The Flexibility team is at the forefront of creating innovative products and tools that enhance energy adaptability. Our flagship product, Intelligent Octopus, automates demand management for 300,000 customers utilizing electric vehicles, home batteries, and smart heating devices. We save 2 million customers money through initiatives like Saving Sessions and Free Electricity Sessions while managing 568 MW of large-scale grid batteries to stabilize the energy system. The solutions we develop are utilized by millions, driving increased renewable energy usage and aiding in the decarbonization of global energy systems.We foster a flat organizational structure and a dynamic, open culture that nurtures innovation, flexibility, and creativity. At Octopus, we embrace authenticity—our team consists of talented individuals who achieve results while remaining true to themselves.If this opportunity resonates with you, we would be thrilled to connect.

Affinidi is a London-based technology company working to reshape digital data ownership. The team creates tools that help individuals and organizations manage their digital identities, always with privacy and security as priorities. Their work centers on decentralized digital identity solutions, aiming to build a trusted network for digital credentials. This approach helps people and businesses exchange data and services safely across industries and borders. Role overview The Senior Backend Engineer (Rust) position focuses on developing backend systems that drive Affinidi’s vision of secure, user-controlled data management. This role requires strong, practical experience with Rust to build and maintain the core infrastructure behind Affinidi’s products. Engineers in this team work on complex backend challenges and are encouraged to find practical solutions to real-world problems. The work supports privacy-first, decentralized identity products that serve a wide range of users and industries. Location This role is based in London, England, United Kingdom.

About Mistral AIAt Mistral AI, we harness the transformative power of artificial intelligence to simplify daily tasks, save precious time, and enhance learning and creativity. Our innovative technology is crafted to seamlessly integrate into the fabric of everyday work life.We are on a mission to democratize AI through high-performance, optimized, and cutting-edge open-source models and solutions. Our robust AI platform is tailored to meet the diverse needs of enterprises, whether on-premises or in the cloud. Our flagship offerings include Le Chat, your AI assistant for both life and work.We pride ourselves on being a dynamic, collaborative team deeply passionate about AI and its potential to reshape society. Our diverse workforce thrives in competitive environments and is dedicated to fostering innovation. With teams distributed across France, the USA, the UK, Germany, and Singapore, we embody creativity, humility, and a strong team spirit.Join us on this exciting journey as we shape the future of AI, making a meaningful impact together. Discover more about our vibrant culture at https://mistral.ai/careers.Role OverviewWe are on the lookout for passionate and talented Software Engineers to join our team. As a Backend Engineer, you will play a pivotal role in developing the core systems that power our key products: AI Studio, Le Chat, and Mistral Code. You will shape how users and developers interact with our AI platform at scale. Your focus will be on building reliable, high-performance backend systems and APIs that support millions of users and developers. Your contributions will directly enhance the user and developer experience, making it more engaging, efficient, and intuitive. We welcome engineers at all levels, from fresh graduates to seasoned professionals who are eager to learn, collaborate, and deliver impactful solutions.Key ResponsibilitiesBased on your expertise, you will engage in crucial components of our technology, including:Backend Development- Design, develop, and maintain scalable and robust backend features and APIs using modern frameworks.- Ensure high performance and reliability across our distributed systems.- Contribute to systems that support authentication, billing, AI tooling, and observability.

We are seeking an experienced and passionate Senior Backend Engineer specializing in TypeScript to join our dynamic software engineering team at onrunning. In this pivotal role, you will lead the design and development of robust backend systems that power our innovative applications. You will collaborate closely with cross-functional teams to deliver high-quality solutions that meet the needs of our users. If you have a strong background in backend development, a love for building scalable systems, and a desire to drive technical excellence, we want to hear from you!

Join Capco as a Senior Backend Engineer specializing in Java and play a pivotal role in designing and implementing robust backend solutions that drive our innovative projects. You will collaborate with cross-functional teams to deliver high-quality software that meets our clients' needs. This is an exciting opportunity for seasoned professionals looking to make a significant impact in a dynamic environment.

Role overview airapps is hiring a Backend Engineer for its London Metropolitan Area team. This role focuses on designing and building scalable server-side applications that support the company’s products and services. What you will do Work closely with colleagues across different functions to develop backend systems Contribute to the architecture and implementation of server-side features Help ensure backend solutions can scale and perform reliably Location This position is based in the London Metropolitan Area.

Join xAI as a Backend & Infrastructure Developer Experience Engineer, where you will enhance our internal developer tools to boost productivity across the organization. Your mission will be to build and optimize applications for debugging local environments, visualizing production data, and accelerating our CI pipelines. We are looking for a passionate and skilled engineer who thrives in a collaborative and innovative environment.

Application Deadline: We are actively conducting interviews and are eager to fill this role as soon as we find the right candidate.ABOUT THE OPPORTUNITYWe are in search of talented Backend Software Engineers who are passionate about developing tools that enhance frontier AGI safety research. This includes creating and maintaining evaluation libraries and tools that enable monitoring and control of our LLM traffic.REPRESENTATIVE PROJECTSAs part of your role, you may work on the following projects within your first six months:Internal tools for efficient running and analysis of evaluations, such as a system that investigates thousands of agentic evaluation runs in parallel and automatically surfaces insights.Automated evaluation pipelines designed to streamline the process from accessing a new model for pre-deployment testing to analyzing key results and disseminating them.Orchestration tools enabling researchers to execute thousands of agentic evaluations in parallel on secure remote machines.LLM proxy services that allow real-time monitoring of our coding agent traffic, supporting automatic identification of undesired behaviors.Development of LLM agents and MCP tools that automate internal software engineering and research tasks, with safeguards to prevent significant failures.Continuous Integration (CI) pipeline optimizations to enhance execution speed and eliminate unreliable tests.Telemetry API and enhanced instrumentation of existing tools to monitor usage and improve reliability.A data warehousing pipeline to store thousands of evaluation transcripts for research and dataset building.Improvements to the Inspect framework and ecosystem, including support for modern agentic scaffolds.