Backend Engineer - Personalization at Spotify | London

Backend EngineerJoin Gradient Labs, where we are revolutionizing customer service standards.Established in 2023, we have rapidly transitioned from concept to a dynamic team, serving clients you recognize and trust. Our AI-driven solution empowers businesses to manage complex customer support challenges with confidence and efficiency, ensuring transparency an…

Gradient Labs creates AI-driven tools for financial services, with a core product that acts as an AI operations agent tailored to the sector. Since its founding in 2023, the company has expanded rapidly, now serving recognized clients and focusing on safe, accurate handling of complex customer inquiries. The team brings together experience from Monzo, Pleo, and Google, united by a drive to solve difficult AI challenges and improve customer operations. Role overview The Product Engineer role in the London office goes beyond software development. Product Engineers at Gradient Labs look for ways to streamline processes, automate repetitive work, and remove obstacles for colleagues. The goal is to build and enhance systems that empower a small team to deliver meaningful results for the industry. What you will do Build the Control Center: Develop the main interface that lets customers configure, manage, and monitor the AI agent’s performance. Design user experiences: Create enterprise-grade interfaces that remain intuitive, aiming for the clarity and usability of products like Notion or Figma. Develop internal tools: Build applications that help the team address customer issues efficiently. Iterate quickly: Contribute in an environment where code is deployed frequently, often several times a day. Work across the stack: Use Go, PostgreSQL, Temporal, and Encore on the backend, with Next.js on the frontend. Location This role is based onsite at the London office.

Join Gradient Labs to Revolutionize Customer Experience in Financial ServicesAt Gradient Labs, we are on a mission to create an innovative AI agent that transforms customer interactions and streamlines operational efficiency within the financial services sector.Established in 2023, we have rapidly progressed from a concept to a dynamic team, serving renowned clients who appreciate our cutting-edge solutions. Our AI agent is distinctive, being the sole AI operations agent tailored specifically for financial services, adept at managing even the most complex and critical customer inquiries with utmost safety and efficiency. It acts as a singular agent for all customer operations, providing businesses with the extensive visibility and control necessary to ensure reliable outcomes.Our team is small but formidable, composed of builders from prestigious organizations such as Monzo, Pleo, and Google. If you are passionate about solving challenging AI problems and wish to influence the future of customer operations and experiences, we eagerly await your application. Your Role as an AI Engineer at Gradient LabsAs an AI Engineer, your primary responsibilities will include:Agent Enhancement: Develop, assess, optimize, and expand the capabilities of our AI agent. This entails preparing datasets, iterating on enhancements, and thoroughly testing and deploying successful methodologies into our production environment.Experimentation & Prototyping: Stay ahead of the curve by keeping up with the latest advancements in NLP and generative AI. You will explore and prototype innovative solutions to integrate state-of-the-art technologies into our platform.Data Analysis: Examine customer query datasets, support tickets, and related information to uncover insights and identify further automation opportunities for our agents. Who We SeekIndividuals eager to challenge the limits of autonomous agents that emulate human behavior.Self-driven professionals who thrive in a fast-paced setting rather than lengthy research cycles.Quick learners who can summarize, replicate, and test ideas from academic research.Impact-driven contributors focused on the practical applications of the products they develop rather than solely on research outcomes.Resilient problem-solvers who can navigate the uncertainties and setbacks that come with experimental work.

Join Gradient Labs in Revolutionizing Financial ServicesAt Gradient Labs, we're on a mission to transform customer experience and operational efficiency through our innovative AI agent tailored for the financial services sector. Established in 2023, our startup has rapidly evolved from a concept to a dynamic team, serving well-known clients with our unique technology.Our AI operations agent stands out as the only solution designed specifically for the complexities of financial services, adeptly managing even the most challenging customer inquiries with safety and precision. More importantly, it acts as a cohesive agent across all aspects of customer operations, providing businesses with the visibility and control they need to trust their outcomes.Our team is composed of passionate builders from top companies like Monzo, Pleo, and Google. If you're eager to tackle some of the most significant challenges in AI and contribute to shaping the future of customer operations and experience, we want to connect with you.

Join Gradient Labs in revolutionizing customer experiences and operational efficiency in the financial services sector.Founded in 2023, Gradient Labs has rapidly evolved from an innovative concept to a dynamic team serving well-known clients. Our unique AI operations agent is the first of its kind tailored specifically for financial services, adept at addressing high-stakes customer inquiries with precision and safety. This all-encompassing agent provides businesses with the visibility and control needed for reliable outcomes across their operations.Our team comprises talented individuals from prestigious companies such as Monzo, Pleo, and Google. If you are eager to tackle complex challenges in AI and contribute to the future of customer operations and experience, we invite you to connect with us. Your Role and ImpactWe are in search of our inaugural Founding Platform & Security Engineer, a dedicated and skilled professional to join our expanding team. In this pivotal greenfield position, you will play a crucial role in designing and securing our advanced AI agent platform and its infrastructure from the ground up.As you report directly to the CTO, you will establish the technical vision for Platform & Security while working closely with AI, engineering, and product teams to effectively scale and deploy our platform across various cloud environments. This role offers an exciting opportunity to leverage your extensive security expertise, particularly within the AI domain, to create enterprise-grade security systems in a fast-paced and evolving landscape.Ownership of Scaling Deployments: Lead the charge on application, cloud, network, and AI agent scalability across our platform, driving the global deployment of our agent across multiple cloud environments.Architect & Implement Security Framework: Design and establish a robust security framework that encompasses customer-facing products, cloud infrastructure (AWS, Azure, or GCP), and enterprise integration points, safeguarding against both traditional and modern AI-enabled threats.Integrate Security within AI: Collaborate with our AI engineering teams to embed security best practices throughout model training, evaluation, and deployment processes, enabling innovation while maintaining safety and responsibility.Automation & Tooling: Enhance security operations through the integration of tools into CI/CD pipelines, ensuring efficiency and effectiveness.

As an AI Delivery Lead at Gradient Labs, you will spearhead the integration of cutting-edge AI solutions, driving innovation and excellence in delivery across our projects. Your role will involve collaborating with cross-functional teams to ensure that our clients receive the highest quality of service and transformative AI capabilities.

About Polygon LabsPolygon Labs is a pioneering global blockchain payments firm dedicated to constructing and managing infrastructure that facilitates instant, reliable, and scalable money transfers. Our mission is to transition all monetary transactions on-chain. We are developing the Polygon Open Money Stack, a cohesive and integrated suite of services and technologies designed to enable seamless and dependable money movement anywhere. Our robust infrastructure has enabled trillions of dollars in on-chain value transfers, supporting millions of daily transactions for some of the world's largest banks, fintech companies, enterprises, and consumer applications.Your RoleAs a Senior Backend Engineer at Polygon Labs, you will be instrumental in developing OMSX, the unified gateway and dashboard for the Polygon Open Money Stack. OMSX serves as the primary interface for developers and enterprises to integrate with Polygon Labs’ financial infrastructure, encompassing payments, wallets, and various on-chain services. This position presents a unique greenfield opportunity to architect and create backend systems from the ground up, handling high-scale infrastructure that processes transaction volumes in the hundreds of millions to billions while shaping the developer experience within the Polygon ecosystem.You will take ownership of significant components of the backend architecture, contribute to key system design decisions, and help lay the groundwork for a platform that empowers global monetary movement.Your ResponsibilitiesYou will be tasked with designing and constructing backend systems that drive OMSX and the broader Polygon Open Money Stack, prioritizing scalability, reliability, and developer experience.Design and implement scalable Go services that manage high-throughput financial workloads.Develop and maintain APIs for integration across various internal services and external financial systems.Create backend systems capable of handling substantial datasets with rigorous performance and reliability standards.Optimize PostgreSQL queries and data models for high-scale production environments.Implement caching techniques and performance enhancements utilizing technologies such as Redis.Contribute to system observability through structured logging, metrics, and monitoring solutions.Collaborate closely with frontend and platform teams to ensure a cohesive developer and user experience.Engage in architectural discussions and make informed decisions regarding system design trade-offs.

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 Aircall, a revolutionary unicorn in the AI-powered customer communications sphere, trusted by over 22,000 companies globally to enhance revenue, expedite issue resolution, and empower customer-facing teams. We are transforming the landscape of customer communications by integrating voice, SMS, WhatsApp, and AI into a unified workspace.Our growth is driven by a straightforward principle: to enable teams to work smarter, not harder. Our AI Voice Agent automates routine calls, while AI Assist simplifies post-call tasks, and AI Assist Pro provides real-time insights, allowing individuals to excel in their roles. This synergy results in increased revenue, quicker resolutions, and scalable teams.Headquartered in Paris, with a solid presence in North America anchored in Seattle, Aircall also has teams in vibrant cities such as Madrid, London, Berlin, San Francisco, New York City, Sydney, and Mexico City. Our product is beloved by customers, and we are rapidly scaling, supported by top-tier investors and continuous AI advancements across multiple product lines.At Aircall, you'll become part of a dynamic company. We are ambitious, focused on product development, and execution-oriented, with a clear impact, swift decision-making, and genuine growth opportunities.Our Work Culture at Aircall: We prioritize customer satisfaction, leverage data for decision-making, and are dedicated to delivering significant outcomes. We cherish ownership, continuous improvement, and thoughtful agility. If you thrive in a collaborative, fast-paced environment where trust and impact are essential, you will thrive here.Position Overview:As a Senior Backend Software Engineer, you will take charge of designing, developing, deploying, and maintaining essential features that enhance customer value on our voice platform.You will be expected to advocate for best practices, mentor team members, and contribute to the broader Engineering community as part of your daily responsibilities.Quality, excellence, and agility are at the core of our delivery process, and you will play a pivotal role in elevating these standards.Utilizing a diverse array of backend technologies tailored to specific needs, all hosted on AWS, we create resilient services that deliver added value on top of voice while fully integrating with our customers' critical business tools (CRM, Helpdesk, E-Commerce, etc.).

Join V7 LabsAt V7 Labs, we're revolutionizing the AI landscape by creating platforms that empower individuals to achieve peak performance with unmatched efficiency. Our goal is to convert human expertise into reliable AI, streamlining complex processes to be quicker, smarter, and more precise. We are experiencing rapid growth, supported by top investors and AI visionaries, including the creators behind Transformers and Gemini.Your RoleAs a Product Engineer, you will contribute to V7 Go, a platform designed to equip legal, finance, insurance, and accounting sectors with a customizable no-code AI agent toolkit. This tool focuses on harnessing multi-modal data to produce verifiable outputs while ensuring transparency in AI logic for accuracy and compliance.V7 Go integrates the latest models, including GPT-5, Claude 4.1, and Gemini 2.5, ensuring optimal accuracy and performance. Check out the V7 Go keynote for more insights into our innovative solutions.Team Dynamics and ImpactYou will report directly to Chris, our Engineering Manager, and collaborate within the Go Engineering team.Working alongside a dedicated team of up to 7 professionals, you will take on significant responsibilities encompassing coding, testing, planning, and analysis.You will have the autonomy to establish your own objectives, strategies, and metrics, emphasizing impactful outcomes rather than mere task completion.We value proactive engineers who take ownership of their work, demonstrating initiative in problem-solving and collaboration.Your Day-to-Day ResponsibilitiesFacilitating the application of foundational models to scale multi-modal data.Enhancing our platform to effectively manage complex multi-tenant usage patterns.Developing a comprehensive suite of APIs to support both our internal systems and customer-facing products.Delivering production-ready updates multiple times daily, collaborating closely with Product and Design teams to address customer needs.Candidate ProfileExperience in functional programming is essential. Familiarity with Elixir is advantageous, but languages such as Scala, GoLang, Node.js, Haskell, Clojure, and F# are also welcomed.Strong problem-solving skills and a proactive attitude towards challenges.

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.

Join our innovative team at reteam as a Backend Engineer! In this role, you will collaborate with cross-functional teams to develop robust backend solutions that power our applications.We are looking for an enthusiastic engineer who is passionate about creating efficient and scalable systems. Your expertise will contribute to enhancing our product offerings and improving user experiences.

About 9fin9fin is a cutting-edge AI platform revolutionizing the global debt markets, which represent the largest asset class exceeding $145 trillion.The landscape of debt markets is extensive, global, and essential, yet it often relies on disjointed data, PDFs, and manual processes. 9fin transforms this outdated infrastructure by providing a unified platform that consolidates proprietary credit data, in-depth analysis, and efficient workflows across international markets.Currently, 9fin empowers over 300 prestigious institutions worldwide, including leading banks, asset managers, private equity firms, law firms, and consulting advisors. The company is experiencing rapid growth, particularly in the US, with exceptional retention rates driven by robust workflow adoption.We are at a pivotal moment. With a validated product-market fit and strong global demand, 9fin is propelling towards becoming the definitive platform for debt markets globally.What You'll Work OnAs a Senior Backend Engineer on our Structured Credit team, you will contribute to the development of our market-leading CLO product and assist in the launch of a new vertical.Our team is dedicated to making a significant impact, leveraging technology to create value for the business. While we have overarching business goals, we enjoy the autonomy to define our team objectives and determine our success metrics. We uphold accountability and proactive behaviors such as ownership.Lead projects within a cross-functional team by defining and designing systems, building proof of concepts, and delivering new service functionalities—including APIs, data processing, and automation—while collaborating with Product and Clients.Engage in backend development and engineering primarily on the services and web applications hosted on the 9fin platform.Play a crucial role within project teams as a senior individual contributor, conducting code reviews, mentoring fellow developers, and participating in early research and experimentation with new technologies to provide insights for new features and products.Continuously enhance the 9fin codebase by seizing opportunities to automate, refactor, and document processes when it has the most significant impact.Work across diverse web platforms involving complex financial data modeling, intricate access control logic, environmental data capture, integration of ML/AI prediction services, and data visualization.

About JuniorAt Junior, we are on a mission to revolutionize the investment research landscape with innovative LLM-powered tools designed specifically for private market investors. Our clientele includes some of the world's leading private equity and consulting firms, collectively managing billions in annual investments. As a profitable and bootstrapped enterprise, we have grown our team to 24 talented individuals across our London and NYC offices, and we achieved a remarkable 10x revenue growth in 2025.Discover more about our mission and values here. Role DescriptionAs our first dedicated Backend Engineer focused solely on our internal go-to-market and operations stack, you will play a pivotal role in shaping our technology framework. Your responsibilities will include:Crafting an AI-first tech stack from the ground up, influencing infrastructure decisions and priorities.Rapidly deploying internal tools and receiving immediate feedback from your team members, who will quickly become your strongest advocates!Developing and managing our data warehouse and internal data architecture.Engaging in innovative projects that leverage LLMs, automation, and advanced agent technologies.Cultivating our engineering culture. Sample Set of ProjectsUser Health Reporting + CRM Data Quality: Automate data pipelines to enhance metrics visibility in BI dashboards and ML evaluations, while establishing alert systems for risk signals.User Feedback Integration: Develop a tool that summarizes user feedback calls, prioritizes feature requests, and communicates findings to our Product team.Billing and Invoicing: Implement complex B2B pricing models encompassing usage-based, seat-based, and platform fees, while automating financial reconciliation processes.Data Warehouse Development: Create a data warehouse to integrate product, CRM, and operational data, and generate tailored dashboards for different teams. About YouWe are searching for a backend/data engineer who...

About 9fin9fin is revolutionizing the global debt markets with its cutting-edge AI platform, catering to the world’s largest asset class valued at over $145 trillion.The debt markets are extensive, international, and essential, yet they are often hindered by disjointed data, PDFs, and manual processes. 9fin transforms this outdated framework by providing a unified platform that consolidates proprietary credit data, in-depth analysis, and streamlined workflows across global markets.Currently, 9fin supports over 300 prestigious institutions worldwide, including leading banks, asset managers, private equity firms, law firms, and advisory companies. Our rapid growth is marked by significant expansion in the US and an exceptional retention rate driven by extensive workflow adoption.We are at a pivotal moment in our journey. With a proven product-market fit and substantial global demand, 9fin is on the path to becoming the definitive platform for debt markets globally.What You'll Work OnYou will lead technical projects, defining and designing systems, swiftly creating proof of concepts, and collaborating closely with Product and our clients.Develop code and guide your team in delivering new service functionalities, implementing APIs, managing data routing/processing, and establishing automation mechanisms.Your primary focus will be on backend services and the web applications that support the 9fin platform.Assume a leadership role within project teams, conducting code reviews and mentoring junior developers, while also participating in early research and experimentation with new technologies to inform new features and products.Continuously enhance the 9fin codebase by automating, refactoring, and documenting when possible.Diversity is key: Our web platforms encompass a wide range of areas, including complex financial data modeling, environmental and energy data capture, integration of ML/AI prediction services, and data visualization and automation systems.Collaboration is vital: We form cross-functional teams for every project, incorporating the necessary domain expertise from 9fin in finance, law, and editorial. Your ability to convey complex projects to non-technical audiences will foster productive and efficient team collaboration.Developer Experience: By managing automated processes and enhancing the development environment, you will help improve the overall experience for developers.

Backend Engineer About OutpostImagine a world where expanding your business globally is as easy as local sales. At Outpost, we are pioneering the AI-driven global trade engine, consolidating all the essential rules to facilitate international sales into a seamless infrastructure. Simply tell us what you’re selling, and we’ll guide you on how to sell it globally.Operating as the Merchant of Record or Tax of Record in over 58 tax jurisdictions, we take on full liability or just the tax layer. From analysis to setup, we absorb the complexities so you can focus on your business.Sell anything, anywhere, without compromise. The RoleWe are looking for a talented Backend Engineer eager to create complex financial infrastructures from the ground up. You will collaborate closely with our engineering leadership to implement payment flows, develop tax calculation engines, and build systems that power international commerce. Your insights will shape product and technical discussions, challenge existing assumptions, and help define our technical direction.Join us in constructing the infrastructure that empowers businesses to sell globally without the typical challenges. You will engage in payment processing, multi-currency ledgers, real-time tax calculations, merchant onboarding, and AI-powered compliance tools. Tackle challenging problems at real scale. What You’ll GetYes, the work can be intense, but you'll be building crucial financial infrastructure that manages hundreds of millions in transaction volume.Your contributions will significantly influence our technical direction, and you'll collaborate with a small team of experienced engineers, helping shape Outpost’s growth. If you're passionate about diving deep into payments, tax, and fintech infrastructure, this is the opportunity for you. What You’ll BuildPayment processing infrastructure capable of handling significant transaction volumesRobust ledger and reconciliation systemsTax calculation engines across multiple jurisdictionsReal-time transaction monitoring and risk management systemsMerchant onboarding and integration frameworksConnections with major e-commerce platformsAI/LLM powered taxation toolsAI/LLM driven fraud and risk management solutions What You’ll Do

Pelago stands at the forefront of virtual healthcare, specializing in Substance Use Management. Our comprehensive program offers personalized guidance, support, and treatment for individuals aiming to overcome challenges related to tobacco, alcohol, and opioid use. We cater to a diverse spectrum of substance use, from unhealthy habits to active disorders, ensuring that each member receives tailored care that aligns with their health, habits, genetics, and personal objectives. Our array of virtual services encompasses educational resources, cognitive behavioral therapy (CBT), and comprehensive medication-assisted treatment (MAT). Pelago empowers employers and health plans to provide accessible and effective solutions for substance misuse. Having successfully partnered with hundreds of employers and health plans, we have positively impacted over 750,000 lives. After recently securing our Series C funding with over $151 million raised from premier global investors, we invite passionate individuals to join our mission of transforming health outcomes.About Pelago Engineering:Our engineering team is composed of empowered, outcome-focused problem solvers who collaborate closely with product, design, and clinical teams to enhance member outcomes at scale.As AI reshapes the software development landscape, we are proactively refining our development processes to prioritize system design and impactful decision-making over rote implementation.How We Work:Outcome-driven: Engineers tackle substantial problems rather than merely building features. Success is evaluated based on learning, impact, and outcomes—not just speed.AI-native: We leverage AI throughout the software development lifecycle to expedite implementation, testing, and reviews, allowing engineers to concentrate on intent definition, behavior validation, and system resilience design.High autonomy, high accountability: Teams enjoy significant ownership of their domains, with autonomy translating to responsibility for quality, safety, and results.Cross-functional collaboration: Engineers work synergistically with Product, Design, Data, and Clinical teams, sharing responsibilities for discovery, experimentation, and delivery.Quality and safety are paramount: Our work is conducted within a regulated domain that directly impacts members, making reliability, observability, and correctness top priorities.What You’ll Do:Instead of traditional task lists, you will take full ownership of significant problem spaces from discovery through to delivery.

Corgi builds insurance solutions for tech startups, using AI to power underwriting and streamline coverage. Backed by $108M in funding and operating as a regulated carrier, the company is expanding across the UK and EU. The platform relies on Django, integrates Stripe for payments, and emphasizes new product development. Role overview This Backend Engineer role is based in London and centers on taking projects from concept to live launch. The team values engineers who build and ship products, not just maintain existing systems. Candidates who have delivered personal projects or launched products with real users will feel at home here. The environment suits those who prefer moving quickly and seeing their work in production without long delays. What matters here Independently developing and launching working products Shipping projects quickly, often within hours or days Comfort working across the stack and tackling new challenges Balancing strong opinions with openness to better solutions Low ego, with motivation driven by results Energy and drive to thrive in a startup setting How the team works Quick decision-making, prioritizing progress over perfection Frequent launches and iterative improvements Products ship and evolve, rather than stalling in review High intensity during launches, with steady momentum at other times Transparency and open decision-making are encouraged Internal competition is seen as a way for everyone to improve This is a hands-on role focused on building. Coasting is not an option. Behaviors that end the role quickly Engaging in office politics, avoiding accountability, or spreading rumors Taking feedback personally instead of using it to improve Choosing complexity when simplicity is possible Missing deadlines after making commitments How to apply Send links to your GitHub, personal website, or live projects Resumes are not accepted Email your application to: sergio@corgi.com If you cannot show delivered work, this role is unlikely to be a fit Location and compensation London-based, with on-site or hybrid options Base salary: £75,000 to £140,000 Equity is available The wide salary range reflects a focus on proven ability to ship, not job titles

Join Herondata as a Principal Backend Engineer and lead the charge in developing robust backend architectures. You will collaborate with cross-functional teams to design, implement, and optimize scalable solutions that support our mission of providing top-tier data services. Your expertise will drive innovation and enhance our platform's performance, ensuring we remain at the forefront of the industry.