Backend QA Engineer in Paris

Join our dynamic team as a Backend Engineer specializing in Rust at connecthum, a pioneering AI infrastructure startup dedicated to constructing the safety and control layers for expansive AI systems.About connecthum:We are an AI-native product company focusing on AI safety and infrastructure.Supported by a diverse range of international investors.Our systems manage high volumes of AI traffic across enterprise environments.We train and fine-tune our proprietary models to ensure optimal performance and reliability.A compact yet highly skilled team that delivers rapid results.Our mission is to create the evaluation and control layer for AI systems, enabling organizations to define, test, and enforce AI behavior in real-world situations.Your Contribution:Design and implement robust Rust backend services that facilitate real-time policy enforcement.Take ownership of features from conception to deployment - including API design, database schema, and monitoring.Develop high-throughput data pipelines to manage extensive AI traffic efficiently.Enhance system performance, reliability, and observability.Collaborate across the stack as needed, prioritizing problem-solving over strict boundaries.Work closely with product, research, and ML teams to drive innovation.This role is hands-on, directly influencing how AI operates in production settings.Technical Environment:Asynchronous Rust (Tokio)Utilizing modern web frameworks such as Axum and ActixPostgreSQL for large-scale applicationsImplementing caching and event streaming architecturesBuilding high-throughput distributed systemsFocus on production observability and performance tuning(In-depth technical stack details will be shared during interviews)Your Expertise:Demonstrated production experience in developing backend systems using Rust.Strong foundation in asynchronous programming and concurrency principles.Excellent system design capabilities, including scalability, failure modes, and trade-offs.Proficient with PostgreSQL and other related technologies.

Join us as a pivotal member of the Backend team at amo, where you'll play a critical role in shaping our infrastructure. In the initial months, you will collaborate closely with the team and gradually take charge of key components and features. At this early stage of our journey, we are in search of adaptable engineers who are eager to contribute across multiple facets of our company’s foundation.We appreciate team members who dive deeply into their areas of expertise, fostering a culture of subject matter mastery within our team. This dedication to specialization is a core expectation for every engineer.Our backend team is responsible for both server-side operations and the backbone of the client, as we believe a unified team can more effectively manage topics like networking, data modeling, management, and synchronization.As a Backend Engineer, your daily responsibilities will include:Building the FutureYou will develop robust systems designed to handle significant traffic, vast amounts of data, and an unparalleled rate of scaling. Your toolkit will include cutting-edge technologies, elegantly crafted code, and systems built for seamless horizontal scaling.Ensuring Cross-Platform CohesionBeyond server-side development, you will be involved in the enhancement and maintenance of a Rust component shared between iOS and Android. This component primarily focuses on networking, data synchronization, and data-oriented feature logic, benefiting from a single codebase. You will collaborate with mobile engineers to ensure a consistent experience across platforms and bridge the gap between mobile development and backend architecture for a cohesive user journey.Innovative Feature DevelopmentEngage in brainstorming sessions to design and implement unique features that distinguish us in the marketplace.Commitment to Continuous ImprovementWe value mutual learning and staying updated with industry trends and emerging technologies, encouraging fresh ideas and contributions to our culture of continuous improvement.Ownership of Your DomainYou will monitor analytics and manage system incidents, taking ownership of your responsibilities and proactively addressing issues and bug fixes.

Join us as a Frontend Engineer specializing in TypeScript and React at connecthum, an innovative AI infrastructure startup dedicated to developing advanced solutions for the safety and management of large-scale AI systems.About connecthum:A pioneering AI-native product company focused on AI safety and infrastructure.Supported by a diverse group of international investors.Expertly handling large volumes of AI traffic within enterprise environments.Creating and optimizing proprietary models for enhanced performance and reliability.A compact, highly skilled team committed to rapid delivery.Our mission is to develop a robust control and evaluation framework for AI systems, empowering organizations to define, test, and regulate AI behaviors in real-world contexts.Your Contributions:Take ownership of and deliver comprehensive product features across the frontend and full stack.Craft user-friendly, high-quality UX designs that simplify complex AI workflows.Develop seamless product flows, from initial onboarding to advanced analytical capabilities.Work collaboratively with founders, product managers, designers, machine learning experts, and researchers.Translate state-of-the-art AI functionalities into dependable user-centric tools.Lead the product development lifecycle while shaping technical direction and product strategies.This hands-on position lies at the intersection of product development, AI, and engineering.Technical Environment:Proficient in TypeScript, React, and Next.js.Utilizing Tailwind CSS for design systems.Integrating with LLM APIs (OpenAI API, function calling, context orchestration).Creating data visualization and analysis interfaces.Building full-stack product architecture.Ensuring effective production deployment and system observability.Your Skills:Demonstrated expertise in TypeScript, React, and Next.js.Experience in developing product features from concept to deployment.Comfortable working with LLM APIs and navigating AI product workflows.Proven ability to collaborate with multidisciplinary teams.

Overview: We are seeking a talented Product Engineer specializing in Backend Development with Rust to take charge of and enhance the foundational systems that ensure AI safety at a large scale. Your role will involve constructing APIs capable of managing hundreds of millions of requests, implementing real-time policy enforcement, and developing high-throughput data pipelines.About UsWhite Circle is at the forefront of AI Safety, creating the essential safety, reliability, and optimization framework for AI systems. Our platform is built on policies—easily understandable natural-language rules that outline appropriate AI model behavior. We automatically test, enforce, and continuously refine these policies on a massive scale.We have secured $11M in funding from leading investors, founders, and executives from OpenAI, Anthropic, HuggingFace, Mistral, DeepMind, Datadog, Sentry, and others.Our systems process over one hundred million API calls each month.We optimize and train our own LLMs to operate more swiftly and cost-effectively than any publicly available or proprietary models.As a compact and highly focused team, we welcome those eager to tackle challenging problems, deliver their work to production swiftly, and actively shape the future of AI safety.Your Responsibilities:Design and implement backend services in Rust that facilitate real-time policy evaluations at scale, ensuring low latency and high reliability.Take ownership of features from inception to deployment: API design, database schema development, and continuous monitoring and iteration.Engage with different layers of the stack as needed; we prioritize problem-solving over rigid role definitions.Enhance system performance and reliability through connection pooling, caching strategies, query optimization, and observability practices.Collaborate directly with product managers, researchers, and ML teams to convert requirements into effective production systems.Ideal Candidate:You have experience building and deploying backend systems in Rust—beyond mere tutorials, you have real-world production experience.You are well-versed in async Rust (Tokio), web frameworks (Axum, Actix), and database interaction patterns.You possess strong system design fundamentals, capable of assessing trade-offs, failure modes, and scalability.You have hands-on experience with PostgreSQL, adept at crafting efficient queries and designing schemas.

Note: This position is based in Paris, France. Relocation and visa support are available if necessary.Achieve the Best Work of Your CareerTrade Republic stands as Europe's largest savings platform, actively engaging in 18 countries and serving over 10 million customers who trust us with more than €150 billion in assets. Our ambition goes beyond that.Our mission is to empower individuals to build wealth through easy, safe, and free access to financial systems. Join us to advance your career while collaborating with exceptional talent and cutting-edge technology, creating a positive impact for millions.Your ResponsibilitiesDevelop and test services and products utilizing modern tools from the JVM ecosystem, including Kotlin, Spring, Vert.x, Hibernate, or jOOQ.Design cloud services with a focus on high availability, low latency, and scalability (primarily on AWS).Implement automated software delivery through GitHub Actions, container-based CI/CD pipelines, and Kubernetes orchestration.Ideal Candidate ProfileA minimum of 5 years of experience in software engineering, preferably within the JVM ecosystem. We welcome candidates from mid to staff level, so whether you are looking to take on more ownership or have extensive experience leading complex systems, we encourage you to apply.Proven experience in developing and deploying scalable features within a service-oriented architecture.A strong dedication to delivering reliable and maintainable software through an iterative development approach and continuous delivery.Experience in building platform services that serve as a foundation for product development (prior experience in platform-focused teams is advantageous).Comfortable working in a flexible hybrid environment, with 2-3 days a week in the office.Why You Should Apply NowOur culture celebrates ownership, excellence, and high energy. We prioritize outcomes and accountability as we strive to tackle one of Europe's significant challenges: closing the pension gap and democratizing wealth. If you resonate with this mission, we want to hear from you!

About Mistral AIAt Mistral AI, we harness the transformative potential of AI to streamline tasks, enhance creativity, and optimize learning experiences. Our cutting-edge technology seamlessly integrates into everyday workflows.We are committed to democratizing AI through high-performance, open-source solutions and state-of-the-art models. Our comprehensive AI platform is tailored to meet the diverse needs of enterprises, available both on-premises and in the cloud. Notably, our offerings include Le Chat, the AI assistant designed to elevate both personal and professional life.As a dynamic and collaborative team, we are passionate about AI's potential to create a significant societal impact. Our diverse workforce thrives in competitive environments and is dedicated to fostering innovation. With teams spread across France, the USA, the UK, Germany, and Singapore, we embody creativity, humility, and a strong team spirit.Join us in shaping the future of AI and make a meaningful impact. Discover more about our culture at https://mistral.ai/careers.Role OverviewWe are in search of enthusiastic and talented software engineers to join our team. As a Backend Engineer, you will play a crucial role in developing the core systems that power our key products: AI Studio, Le Chat, and Mistral Code. Your contributions will shape the way users and developers interact with our AI platform at scale. You’ll focus on building reliable, high-performance backend systems and APIs that cater to millions of users and developers. Your work will greatly enhance both developer and user experiences, ensuring they are engaging, efficient, and intuitive. We welcome engineers of all levels, from recent graduates to seasoned professionals, who are eager to learn, collaborate, and deliver impactful solutions.Key ResponsibilitiesDepending on your expertise, you will engage with critical components of our technology, which may include: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.

About FinaryAt Finary, we are redefining the investment landscape by empowering individual investors with a comprehensive platform for asset tracking, budget management, investment opportunities, and financial education.Since our inception in 2021, we have rapidly grown to serve over 600,000 users. In September 2025, we successfully raised €25M in a Series B funding round led by PayPal Ventures, with notable support from Y Combinator, Hedosophia, Speedinvest, and industry leaders from Qonto, Photoroom, Bitpanda, UBS, and Wise.We prioritize user experience, performance, and the development of products that significantly enhance financial well-being.TL;DRAs a Staff Software Engineer, you will design and develop high-performance backend services in Rust for our fintech platform, catering to over 600,000 users. You will collaborate with a talented team of 6 Rust engineers across various squads, focusing on investment products, cryptocurrency, or life insurance infrastructure.

About MorphoMorpho is at the forefront of Decentralized Finance (DeFi), operating a cutting-edge lending protocol that has recently garnered $50 million in funding from renowned investors, including Ribbit Capital, a16z crypto, and Coinbase Ventures. Our vision is to create an open lending network that democratizes access to the best financial terms for all. With over $10 billion in deposits, Morpho is rapidly redefining the standards of DeFi lending. We are expanding our team to solidify our position as a key player in the emerging internet-native financial ecosystem.Our MissionAt Morpho, we believe in empowering human ambition by providing open access to capital. The current financial landscape is fragmented, leaving many opportunities unseen and many individuals overpaying or entirely excluded. We strive to ensure that capital flows efficiently to where it is most needed, enabling anyone, anywhere, to access optimal terms.LocationThis role can be based in Paris or remotely (candidates located between -5 GMT and +2 GMT are encouraged to apply to ensure effective collaboration with our team).Our Work CultureWe thrive in a fast-paced environment where tackling challenging problems is the norm. As we navigate this evolving market, adaptability is crucial. We foster a culture of open communication where questioning decisions is encouraged. Our team maintains high standards while supporting each other to overcome obstacles and share knowledge. To learn more about our values, visit morpho.org/jobs.Role & ResponsibilitiesAs a Backend Engineer, you will be responsible for designing, building, and maintaining high-performance backend services and APIs that are crucial to Morpho’s user-facing features. Depending on your level of experience, you may take ownership of specific backend domains, mentor junior engineers, and contribute to cross-team initiatives.Your Responsibilities Include:Develop, deploy, and maintain backend services using TypeScript/Node and GraphQL, ensuring reliable and low-latency experiences for users.Design and optimize relational data schemas (PostgreSQL) for accuracy, performance, and maintainability.Collaborate with cross-functional teams including frontend, product, protocol, risk, and security to deliver seamless integrations.

Trade Republic Bank is looking for recent graduates to join the Backend Engineering Program in Paris. This team builds and maintains the core systems behind Europe’s leading savings platform, which serves over 10 million customers across 18 countries and manages more than €150 billion in assets. This program offers a hands-on introduction to backend engineering in a high-impact, real-world setting. Graduate engineers work alongside experienced developers who provide mentorship and support as you move from academic knowledge to building production-ready systems. What you will do Contribute to backend services using modern JVM technologies such as Kotlin, Java, and Spring Assist in designing and developing scalable, reliable systems Work with APIs, databases, and service-oriented architectures Learn to write clean, maintainable, and well-tested code Collaborate with Product and Engineering teams to deliver features for users Gain exposure to cloud infrastructure (AWS), containerization, and CI/CD pipelines Help debug, monitor, and improve system performance Gradually take ownership of well-defined technical projects Learning and growth Participants will see how backend systems are built, deployed, and scaled in a live production environment. The program is designed to help you develop practical engineering skills while contributing to projects that matter to millions of users.

About the Role airapps is looking for a backend engineer to help build and maintain the systems behind our applications. This position is based in Paris and focuses on developing backend solutions that scale and perform reliably. What You Will Do Design, implement, and maintain backend systems for airapps products Work closely with teammates to solve technical challenges Contribute to a collaborative team environment Who We’re Looking For Experience building backend systems Comfort working with others to solve problems Interest in developing efficient and scalable solutions This is a full-time role in Paris. If building reliable backend infrastructure with a team sounds appealing, airapps would like to connect.

About the APM Data Hub Team The APM Data Hub sits at the heart of Datadog's Application Performance Monitoring suite. This team builds and maintains a backend pipeline that processes, transforms, and routes tracing data at scale after ingestion. The pipeline supports not only APM Distributed Tracing but also a growing set of Datadog products that rely on rich trace data. Role Overview: Engineering Manager I – APM Backend Based in Paris, this role leads a distributed team of 6 engineers. The manager sets the technical direction for a platform that is central to Datadog's product ecosystem. Responsibilities include defining the roadmap for tracing data processing, making trace data accessible to internal consumers, and upholding strong engineering standards for a system that must run reliably at scale. What You Will Do Guide and support a diverse engineering team working on backend data pipelines Shape the technical vision and roadmap for trace data processing Ensure the platform meets high reliability and engineering standards Facilitate collaboration with other product teams that depend on trace data Address complex engineering challenges that affect multiple Datadog products Workplace and Culture Datadog values in-person collaboration and creativity. The company supports a hybrid work model, helping employees balance office life and personal needs.

About PreludeAt Prelude, we are pioneering a new standard for user onboarding and authentication in an era where trust, speed, and conversion are paramount.Our innovative solutions streamline user verification, enhancing security and efficiency while transforming authentication into a strategic advantage. Our flagship product boasts the highest price-to-conversion ratio for OTP code delivery, intelligently adapting to utilize the most effective channels in real-time—whether through optimized SMS routing or popular messaging applications like WhatsApp. Additionally, Prelude actively mitigates spam and fraud risks that traditional providers often overlook, thereby safeguarding both profit margins and user experiences.Established in 2022 and supported by prominent venture capital firms, Prelude has rapidly achieved significant market traction and robust financial health, catering to fast-growing companies throughout Europe and making strides into the US market. Authentication is merely the beginning of our journey.With a forward-thinking roadmap and a suite of market-defining products in the pipeline, we are developing a scalable trust platform that empowers businesses to effortlessly onboard users, combat fraud intelligently, and expand confidently across the globe.About Our TeamThe Prelude team consists of former Zenly professionals who have experienced the limitations of current authentication systems firsthand. While developing products that serve millions, we recognized the challenges posed by costly and unreliable SMS authentication, leading to the inception of Prelude.Currently, our team of 40 is based in Paris, dedicated to creating high-performance, secure user onboarding solutions for businesses in Europe and the US. We believe that small, highly skilled teams are more effective than large, fragmented organizations, and we prioritize impact, quality, and agility.We embrace a flat organizational structure that enhances in-person collaboration, facilitating rapid idea exchange, grounded decision-making, and full ownership of our projects.Our core values guide our daily operations:CareWe are deeply invested in our customers, our colleagues, and the quality and reliability of our products.

Join us at iliad-free in Paris as a Staff Engineer specializing in Python. You will take on a pivotal role in our ambitious program aimed at modernizing and evolving our backend systems.Your primary responsibility will be to lead the technical direction of our information system backend, which manages all Free subscribers, including subscription processes, subscriber spaces, and additional services such as video streaming and mobile phone sales.In this role, you will develop a deep understanding of complex business processes executed by our system, such as billing for third-party services, subscription management, and fiber optic connections.You will guide the team in defining the architecture of this distributed system while actively contributing to development using Python, ensuring hands-on involvement.Your expertise will drive development practices that prioritize resilience, quality, testability, and speed of delivery. Additionally, you will be instrumental in establishing robust operational methods in a model where development teams manage their solutions in production, with a constant focus on performance and scalability.

About UsPhotoroom was founded in 2020 after joining Y Combinator and has rapidly become the leading AI photo editing solution worldwide. We aim to empower users to create professional-grade product images in just minutes.With over 300 million downloads and an impressive annual processing of over 5 billion images, we cater to individual creators and major corporations such as Amazon, DoorDash, and Decathlon through our B2C application and B2B API services.We are a profitable, remote-friendly organization that has successfully secured Series B funding while striving for a remarkable 40% annual growth. Our dedicated team of over 100 innovators focuses on craftsmanship, creativity, and teamwork to deliver significant impact for entrepreneurs and businesses globally. We're on the lookout for a talented Rust software engineer to advance the development of cross-platform libraries that enhance our Android, iOS, and Web applications! This is a pivotal opportunity to work within the engineering team, influence all versions of a product used by millions, tackle intricate challenges, and significantly improve the experience for our users and Photoroom. Salary: €90,000 - €130,000* + Stock Options/BSPCE Enjoy flexibility: work from anywhere in Europe, visit Paris once a month (fully reimbursed), or come to the office more frequently. We provide substantial relocation assistance (up to €10,000), including help in finding housing in Paris and support with visa procedures. Enjoy company retreats twice a year, weekly Happy Hours, and game nights. Our international team operates in English, and we offer language courses for those wishing to learn (English & French).*We can offer higher salaries for exceptional candidates and adjust based on local living costs if necessary. About the Role You will develop the cross-platform libraries that drive Photoroom on iOS, Android, and the Web, making a direct impact on millions of users.You will architect, develop, and implement complex features for in-house app developers using cutting-edge technologies such as Rust, WebAssembly, and wpgu.You will take ownership of your projects from inception to completion: from specifications and implementation to integration on the target platform, collaborating closely with our product management and design teams.

Join Arago and the AragoniansAt Arago, we are a pioneering AI and computer hardware firm dedicated to advancing history through technological innovation. Our mission is to propel breakthroughs at the intersection of artificial intelligence and semiconductor technology.Founded in 2024 by a team of accomplished AI researchers and physicists, Arago combines expertise in photonics, electronics, software, mathematics, and machine learning. Our lean, diverse team hails from top companies and renowned research institutions around the globe.With employees representing nine nationalities and operating from strategic locations in France, North America, and Israel, we are driven by our commitment to excellence and rapid progress. Our guiding principles include:Deliver excellence: We take pride in our work and its impact.Act with urgency: We prioritize speed and efficiency.Foster unity: We build relationships based on trust, respect, and teamwork.With strong backing from leaders at Apple, Arm, Nvidia, Microsoft, and Hugging Face, along with significant support from leading deeptech venture firms in the US and Europe, we are poised for remarkable growth.

Join our dynamic team at Iliad as a Backend Python Developer in Paris! We are looking for passionate and skilled individuals to contribute to our innovative tech projects. You will work closely with cross-functional teams to design and implement robust backend systems, ensuring high performance and responsiveness to requests from the front-end.Key Responsibilities:Develop and maintain server-side applications using Python.Collaborate with front-end developers to integrate user-facing elements.Optimize applications for maximum speed and scalability.Participate in code reviews and contribute to team knowledge sharing.Stay updated with emerging technologies and best practices.

airapps is hiring a Backend DevOps Engineer in Paris. This position centers on building and maintaining systems that keep backend services running smoothly and reliably. Role overview The Backend DevOps Engineer will design and implement solutions to help backend services scale and remain dependable. Collaboration with both development and operations teams is key, with a focus on improving workflows and boosting system performance. What you will do Create and maintain scalable infrastructure for backend services Work alongside developers and operations staff to streamline processes Identify opportunities to enhance system reliability and efficiency Location This role is based in Paris.

About UsAt Yubo, we are revolutionizing the way individuals connect online through our innovative Social Discovery app. By removing likes and follows, we empower our users to form authentic relationships and express their true selves.We have pioneered a fresh approach for Generation Z to engage socially in the digital realm, currently serving millions of active users. Our mission is to continuously redefine how social connections are formed now and in the future.Our team is diverse, multicultural, and passionately dedicated to our vision. As a leading platform for online socialization, we prioritize creating a safe digital environment for our community. Safety is ingrained in our values, and we proactively work on user protection, support, and education, collaborating with the tech industry and NGOs to establish best-in-class child protection standards.Join us on this exciting journey and play a vital role in shaping the future of social interactions!Role OverviewAs we expand our Tech organization for 2026, Yubo is launching a new Innovate squad dedicated to daring product initiatives and high-stakes projects.This squad aims to take bold risks, experiment with ambitious features, and validate ideas through ongoing testing.We are seeking a Senior Backend Engineer to become a key member of our Backend Experience team, reporting directly to Armand, our Engineering Manager.You will work within a multi-disciplinary squad (including Product, Mobile, Design, and Data) alongside a Senior Backend Engineer who shares leadership responsibilities.Your mission? Design, implement, and manage high-risk backend experiments that test groundbreaking product ideas while ensuring our systems remain resilient, scalable, and cost-effective throughout rapid iteration cycles.This position is not about maintenance; it's focused on building, testing, rolling back, iterating, and learning swiftly.

BlaBlaCar’s Payment Squad is seeking a Backend Engineer based in Paris. This team plays a key role in building and enhancing the systems that process payments throughout the platform. The work ensures millions of users can complete transactions smoothly and reliably. Main responsibilities Design, develop, and maintain backend services for payment processing Collaborate with fellow engineers to create scalable technical solutions Contribute to making transactions more reliable and efficient for users Team collaboration This role involves close teamwork with experienced colleagues. Sharing ideas and tackling technical challenges together is a regular part of building and improving payment features at BlaBlaCar.