Senior Full-Stack Developer - ReactJS/Redux at Altersolutions | Paris

Located in the vibrant heart of Paris, Winamax is at the forefront of the online gaming industry. As a leader in poker and sports betting in France, we boast a community of 350,000 players and 600,000 monthly bettors. Our presence extends to Spain, Germany, and soon to Italy and Portugal. We are dedicated to providing our players with an exceptional experience that is technical, creative, and high-quality. Our core values of innovation, unity, and belonging foster a unique multicultural corporate culture.Imagine building your future in gaming!Technically, Winamax is:• A powerful and innovative gaming engine: dynamic adaptation of game offerings, highly configurable poker games, fraud detection.• A distributed and scalable architecture designed to handle real-time platform streams.• A modular platform that meets high availability and data security requirements, capable of managing significant traffic.ABOUT THE ROLEAs a member of our Tech team, you will play an active role in the development of the next generation of Winamax applications (desktop and mobile) and enhancing our cross-platform engine.This position is part of the Casino team responsible for developing Casino game clients (iOS, Android, Windows, Mac, Linux, Web).As a Senior Full-Stack Developer, you will be instrumental in designing, developing, and deploying our applications. Your responsibilities will include:• Developing innovative and scalable features for both front-end and back-end.• Producing robust code for real-time gambling applications.• Managing end-to-end processes: specifications, development, testing, and deployment.• Continuously improving software architecture and development best practices.

UpSlide is the leading productivity and branding solution for financial services. Our innovative software significantly enhances the functionalities of PowerPoint, Word, Excel, and Power BI, enabling users from prestigious firms such as Citi, KPMG, and BNP Paribas to focus on high-value tasks rather than formatting or manual data entry. With over 160 employees, we are in a growth phase, with offices located in Paris (headquarters), London, New York, Singapore, and Berlin.Our Core Values Our values guide our approach to work and are central to our recruitment process. We seek individuals who resonate with the following principles:Excellence: Every detail matters, and we prioritize the quality of our deliverables.Trust: We are passionate, committed, and empowered to act autonomously.Well-being at Work: We maintain a positive outlook and share our enthusiasm with colleagues and clients alike.The Team ‍‍You will join the UpSlide development team, currently composed of 26 developers organized into 5 squads. Our missions for 2026 include:OfficeJS: Preparing UpSlide for the transition from Microsoft Office to Office JS.FA: Enhancing our product's superiority in the Financial Advisory sector.FA & AI: Strengthening our product's edge in Financial Advisory by focusing on AI-related solutions.IB & AM: Continuously improving our offerings for Investment Banking & Asset Management.Platform: Upgrading our infrastructure to support tenfold user growth.Join Us!

Join Margo Group as a Full Stack Developer specializing in Java and React. We are seeking a talented and motivated individual to contribute to our innovative projects and help shape the future of our tech solutions. As part of our team, you will work closely with designers and product managers to refine our offerings and deliver high-quality software solutions.

About UsAt CryptoNext Security, we are pioneers in the realm of deep technology, focusing on post-quantum cryptography. Our innovative solutions empower businesses and institutions to safeguard their data against the impending challenges posed by quantum computing. We proudly collaborate with prominent clients across sectors such as finance, defense, and telecommunications.Your Daily ResponsibilitiesCraft and implement dynamic user interfaces utilizing React for our advanced post-quantum cryptography products.Work collaboratively with Product and Backend teams to deliver a seamless and user-friendly experience.Enhance performance while ensuring cross-browser and cross-device compatibility.Integrate REST APIs to facilitate interaction with backend services.Engage in code reviews and uphold best practices, including unit testing, continuous integration, and comprehensive documentation.Propose enhancements to frontend architecture through technological upgrades and refactoring.Foster improvements in our products beyond your typical responsibilities.Adhere to our frontend team principles: “Done over perfect” / we prioritize speed: KISS, DRY (Don't Repeat Yourself), SOLID.Essential SkillsProficient in React / Next.js along with its ecosystem (React Hooks, Context API).Solid understanding of TypeScript and fundamental programming principles.Experience with modern UI libraries such as Tailwind or chadcn/ui.Proven track record in integrating REST APIs.Strong knowledge of frontend performance optimization and related tools (Webpack, Vite, Core Web Vitals).Familiarity with frontend testing frameworks like Jest, React Testing Library, and Cypress.Competence in Git, CI/CD pipelines, and DevOps for automated integration and deployment.Desirable SkillsExperience with gRPC.Understanding of secure coding practices and application security.Basic knowledge of cryptography and cybersecurity.Experience in a startup or deeptech environment.Join Our TeamYou will become a key member of our R&D team, collaborating closely with backend developers, product managers, and UX/UI designers. You will report to the team lead and work with various departments to develop high-performance, user-centric interfaces that align with our clients' needs.Application ProcessInitial conversation with our HR team to discuss your background and motivations.Technical interview to assess your skills and fit for the role.

About UsCryptoNext Security is a pioneering deeptech startup focused on post-quantum cryptography. We empower institutions and enterprises to navigate a future where quantum computing poses a threat to existing cryptographic standards. Our collaborations span major sectors including finance, defense, and telecommunications, as we deliver state-of-the-art, quantum-safe security solutions.Your RoleIn your capacity as a Full Stack Developer, you will play a key role in advancing DISCOVERY, our innovative observability and orchestration platform tailored for post-quantum cryptography operations.You will engage with the entire technology stack — developing backend services, managing data flows, and crafting frontend interfaces — while working closely with product, backend, and infrastructure teams.Responsibilities Design, develop, and maintain comprehensive full-stack features for the DISCOVERY platform. Create modern, responsive React front-ends that integrate seamlessly with Node.js and Kafka backends. Participate in architectural discussions and propose technical enhancements in line with our long-term product vision. Backend Development & APIs Design and implement efficient REST and event-driven APIs. Ensure optimal performance, scalability, and resilience across distributed components. Collaborate with backend engineers on domain modeling, API contracts, and data flows. Data Visualization & Observability Implement advanced data visualization and monitoring features using the ELK stack (Elasticsearch, Logstash, Kibana). Integrate backend logs, metrics, and analytics into user-friendly frontend dashboards. Engineering Standards Engage in code reviews and maintain high standards of engineering excellence. Contribute to technical documentation and advocate for software craftsmanship. Adhere to the KISS, DRY, SOLID principles, and embrace pragmatic engineering methodologies (“done is better than perfect”). DevOps & CI/CD Assist in deployment workflows, CI/CD pipelines, and automation initiatives. Work within Docker/Kubernetes environments to ensure smooth delivery of applications.

Join our dynamic technical team of around thirty professionals in a warm and fun work environment! You have the freedom to choose your preferred workstation setup, allowing you to work in the way that suits you best.Your day-to-day will involve tackling a diverse range of challenges, including API development, implementing new features, creating proofs of concept (POCs), and managing application maintenance (TMA).Our technology stack includes:NodeJs & ExpressJS;AngularJs, VueJs;MongoDB, Postgres;Kubernetes & Docker;AWS;

Join our innovative team at myjobcompany1 as a Full Stack Web Developer. In this role, you will be responsible for designing and implementing robust applications that improve user experience and meet business needs. You will work with both front-end and back-end technologies, ensuring seamless integration and performance.

Join Outsight, where our cutting-edge software transforms 3D LiDAR data into actionable insights for tracking the movement of individuals and vehicles. Our solutions are utilized by a variety of transportation hubs, including airports and train stations, as well as sports venues, road infrastructures, and industrial sites. We empower operators with precise and anonymous Spatial Intelligence data to enhance operational efficiency and ensure user safety and satisfaction. Our diverse team of experts, spanning across Paris, San Francisco, Sophia-Antipolis, and Hong Kong, is dedicated to advancing our innovative solutions. With a commercial office in Spain, we are committed to our global outreach. Discover more about us through this link: Insights about Outsight. Trusted by leading airports and train stations worldwide, our Passenger Flow Traffic Monitoring solution is a cornerstone of our offerings. Our Car Traffic Remote Monitoring product has also gained the confidence of Tier 1 clients, including BMW. Role Overview We are seeking a vital contributor to our Outsight Shift product suite. Our ecosystem encompasses real-time 3D monitoring of digital twins, live analytics, and decision support tools designed to optimize user management of people and vehicle flows. In this role, you will play a crucial part in architecting our application and frontend foundations to ensure scalability as our product capabilities expand. You will emphasize design, performance, usability, and maintainability while collaborating closely with product managers, data engineers, and scientists to deliver seamless user experiences.

Join our dynamic team at Magellan Partners as a Full Stack Java Developer! In this role, you will be responsible for designing, developing, and maintaining innovative software applications using Java technologies. You will work collaboratively with cross-functional teams to deliver high-quality solutions that meet our clients' needs.As a Full Stack Developer, you will leverage your expertise in both front-end and back-end development to create user-friendly applications. This is an exciting opportunity to enhance your skills and contribute to impactful projects in a fast-paced environment.

At Algolia, we are at the forefront of AI-powered search technology, enabling over 17,000 businesses to deliver rapid and predictive search experiences at scale. Each week, we process more than 30 billion search queries — surpassing the combined total of Microsoft Bing, Yahoo, Baidu, Yandex, and DuckDuckGo.In 2021, we secured $150 million in Series D funding, elevating our valuation to an impressive $2.25 billion. This strong financial foundation allows us to continuously enhance our market-leading platform, serving incredible clients such as Under Armour, PetSmart, Stripe, Gymshark, and Walgreens.The TeamThe Frontend Experiences (FX) team is dedicated to inspiring and empowering Algolia users in crafting exceptional UI experiences powered by Algolia. We envision, develop, and decompose advanced UI experiences into modular elements ready for integration into our users' applications. Our suite of UI libraries, including Autocomplete, is widely utilized, even appearing in the Tailwind and React documentation. Additionally, we maintain the InstantSearch library platform, unlocking complex and modern search and discovery applications.Our approach is framework-agnostic; we utilize various frameworks, including Vue.js and React, as well as plain JavaScript (Vanilla JS). We prioritize quality, writing specifications for every feature we release. Our codebase is in TypeScript, fully open-source, and thoroughly tested.Beyond frontend development, we also handle specific backend functionalities that enhance our user experiences, utilizing TypeScript, Go, and Python.The OpportunityWe are seeking a Full-Stack Engineer to join our Frontend Experiences (FX) team at Algolia. In this role, you will significantly influence the design and functionality of Algolia-powered user interfaces. You will assist customers in reimagining the future of how people search for and discover information. Your contributions will be crucial in architecting our platform, which serves as the face of Algolia’s Developer Experience.Your responsibilities will include:Architecting, designing, and developing new iterations of the InstantSearch platform, alongside our open-source libraries and backend APIs.Designing and implementing features that utilize agentic patterns within the Algolia platform and our open-source libraries.Developing new features, troubleshooting issues, and analyzing user feedback for our well-regarded open-source projects.Collaborating with product, design, and marketing teams on the rollout of new projects and websites.Taking ownership of projects, researching, exploring, and delivering innovative experiences.Sharing your expertise to enhance our understanding and improve search and discovery capabilities.

Who Are We? Safran.AI (formerly Preligens) specializes in advanced artificial intelligence solutions designed for analyzing high-resolution satellite imagery, full motion video (FMV) streams, and acoustic signals. Our innovative tools are deployed across the aerospace, defense, and governmental sectors. Since 2016, the company has been at the forefront of developing complex algorithms and software that automate the analysis, detection, and identification of military-relevant objects using both commercial and governmental data sources. As a part of the Safran group since September 2024, Safran.AI is also instrumental in transforming the group by applying AI solutions to Industry 4.0 domains. For instance, automated image analysis can assist inspectors in identifying potential anomalies in critical components from digital photographs. At Safran.AI, innovation and the pursuit of a safer world are embedded in our culture. Joining our team means collaborating with passionate, multi-disciplinary experts (engineers, researchers, developers) who are driven by a shared commitment to technological excellence. We foster a stimulating work environment where creativity and initiative are encouraged, and every idea is valued. Your Mission, Should You Choose to Accept It As a Full Stack Developer, you will be instrumental in the design and ongoing development of our product and infrastructure, primarily utilizing Python, PostgreSQL, and other cutting-edge technologies. → Design, develop, and maintain our back-end infrastructure and automated pipelines.→ Create, maintain, and evolve user interfaces (JS/CSS) for partner plugins.→ Collaborate with the team on specifications, testing, and technical best practices.→ Work closely with all teams and subject matter experts to understand end-user needs.→ Ensure high code quality for our frameworks by applying best practices and mentoring others. Technology Stack:Our development teams primarily use Python for back-end development and JavaScript (React) for front-end solutions. We also leverage Docker for deployment and SQL/PostgreSQL for database management.

Company Overview:Tessan is a fast-growing French startup specializing in telemedicine, dedicated to combating medical deserts across France. With over 1,500 devices deployed in less than six years, our mission is to ensure that every French citizen can access a doctor within 15 minutes of their home.We are expanding our team to support our product growth and accelerate our technological projects in web, mobile, data, and AI solutions. We are looking for a Full Stack Developer Intern (H/F) to join our technical team and actively contribute to the development of our digital solutions.Key Responsibilities:In a context of rapid product growth and technological innovation, you will participate in developing and enhancing our applications and services. You will collaborate with the technical team on various topics ranging from product development to optimizing our data and AI tools.1) Product Development (Web & Mobile)Engage in continuous development of the Tessan mobile and web applicationsContribute to the creation of new features (front-end & back-end)Assist in bug fixing and ongoing improvements of the applications2) Service Maintenance & ImprovementParticipate in maintaining the backend services and APIsContribute to enhancing performance and stability of servicesHelp establish best development practices (testing, code quality, documentation)3) Optimization & AutomationAssist in optimizing technical and operational processesParticipate in automating workflows (data handling, synchronization, processing)Utilize AI tools to improve productivity and development efficiency4) CI/CD, Deployment & IndustrializationContribute to improving CI/CD pipelinesAssist in deploying and industrializing new projectsHelp implement monitoring tools and service tracking5) Architecture & Technical ProjectsEngage in architectural discussions (mobile, web, backend)Enhance skills on technical choices and best development practicesContribute to data-related projects, data pipeline, and topics around Big Data and AI as projects progress6) Cross-Department CollaborationWork collaboratively with product, operations, and business teamsParticipate in technical discussions and progress meetings with the team

Who are we?At MARGO, our consultants focus on what truly matters: tackling complex projects that combine intellectual challenges with real business impacts. We support major players in finance, industry, and technology in designing and developing high-performance software solutions, including distributed architectures, cloud platforms, real-time systems, and large-scale critical applications.Why join the Software Engineering Practice?You will be part of a team led by Paul Blois, Practice Manager at MARGO for five years. Working alongside them means benefiting from in-depth company knowledge, receiving close support for your career development, and contributing to demanding IT projects with significant impact for our clients.Your Responsibilities- Design, develop, and optimize a new web application for the reporting, tracking, and auditing of insiders (staff with access to sensitive information) for a major banking client.- Participate in defining and implementing a high-performing and scalable architecture.- Address performance optimization challenges in both front-end and back-end systems.- Ensure code quality, maintainability, and security of the solution.- Collaborate closely with product, security, and infrastructure teams for seamless integration.- Contribute to code reviews, continuous improvement, and the sharing of best practices.Languages: Java 17, TypeScriptAssociated frameworks and technologies: Spring Boot, Angular 12, Git, CI/CDChallenges: performance, response time optimization, robustness, and regulatory complianceDesired ProfileWe are looking for a full-stack developer who is passionate about real-time systems and interested in financial markets, eager to work in complex and high-performance environments.- Education level: Master’s degree (engineering school or university).- Strong skills in both back-end and front-end development, multithreading, performance optimization, and good development practices (SOLID, unit testing).- Experience in developing critical systems, real-time data stream processing; experience in finance is a plus.- Ability to solve complex technical problems.

Role Overview Prelude is looking for a Full-Stack Engineer based in Paris, France. This role involves building and maintaining both front-end and back-end features for our applications. The work touches every layer of our systems and directly shapes how users interact with our products. What You Will Do Develop new features across the stack, from user interfaces to server-side logic Maintain and improve existing code to keep applications reliable and efficient Apply software development best practices in daily work Collaborate closely with developers, designers, and product managers to deliver solutions that address real user needs Contribute to our agile development process and help the team adapt as we grow Tech and Collaboration This position offers the chance to work with modern technologies and frameworks. Teamwork is central: engineers, designers, and product managers work together to solve problems and build new features.

Join Altersolutions as a talented .Net / React JS Developer and take your career to the next level! We are seeking an individual with a strong background in .Net and React JS to contribute to exciting projects in a dynamic environment. You will collaborate with a team of professionals dedicated to delivering high-quality software solutions.

Front builds a platform that helps businesses manage the complex demands of B2B customer operations. The product connects teams, tools, and customer conversations so companies can scale without losing the personal touch. Over 9,000 businesses use Front, including names like Uber Freight, Navan, and Stripe. Front is backed by investors such as Sequoia Capital and Salesforce Ventures, with $204 million raised. Support also comes from executives at Atlassian, Okta, Qualtrics, Zoom, and PagerDuty. The company has received recognition including Built In's 100 Best Midsize Places to Work in SF 2025, Top Places to Work by USA Today 2025, and #4 on Fortune’s Best Workplaces in the Bay Area™. The Workflows pod focuses on turning complicated processes into streamlined, automated workflows. This helps customers reach operational excellence by simplifying how work gets done. What you will do Collaborate with product managers, designers, and fellow engineers to build new solutions for the Workflows pod.

Who Are We?Xcelirate is at the forefront of technology, creating innovative platforms that serve thousands of users every minute! We pride ourselves on cultivating an environment where leading developers collaborate to strategically plan and swiftly execute initiatives that solidify our market leadership and fuel our global expansion. Our decade-long growth is a testament to our dedicated customers and the talented team that drives this success.What Are We Looking For?We are seeking a Principal Full-Stack Engineer who has not only navigated the complexities of software development but also played a pivotal role in shaping architectural decisions. Your extensive experience means you view programming languages as mere tools that facilitate the translation of ideas into executable code—selecting them based on practicality rather than trends. You understand that innovation comes from progress, not just novelty.Your journey has equipped you with a wealth of knowledge, including when to abandon outdated practices and embrace more efficient solutions. You are deeply engaged in coding, preferring to remain close to the technology rather than stepping into management roles unless necessary.With a calm and methodical approach to problem-solving, you bring stability to any project. When you join a team, chaos subsides, making way for clearer decision-making and improved collaboration. Your intuitive grasp of key concepts such as optimization and lazy initialization is impressive, and your ongoing home lab projects showcase your curiosity and passion for continuous learning.If this resonates with you, consider applying for this role!What Will You Be Doing?Manage your time effectively while aligning with company priorities.Take ownership of complex engineering challenges from initial problem identification through design, delivery, and iterative improvements.Ensure critical platform components remain reliable, efficient, and maintainable.Develop new features and enhance existing functionalities across our platforms.Refactor codebases to improve performance and maintainability.

Join Alten as a Full Stack Developer specializing in Vue.js and PHP Laravel. We are seeking passionate developers who thrive in innovative environments. You will work on exciting projects that challenge your skills and allow you to grow professionally.

Join CAPFI Technology - a Hub of IT and Financial ExpertiseCAPFI Technology, located in Paris and London, combines our expertise in IT and market finance. Our consultants collaborate with clients on strategic projects that integrate innovation, technology, and financial challenges. Your Responsibilities :As a .NET Developer / Software Engineer (H/F), you will be part of an agile team working with a financial market client on:Developing containerized full-stack applications and micro-services while adhering to Craftsman practices (TDD, BDD, DDD).Analyzing architecture to identify improvements.Designing and developing .NET applications.Implementing continuous integration via automated tests (Jenkins, GitLab, Bitbucket, etc.) and continuous deployment (Ansible, AWX, Octopus, GitLab, etc.).Managing versions (Git, TFS).Creating test plans and participating in tests not covered by unit tests. Your Strengths :A passion for thriving in a demanding and enriching environment.A desire to challenge yourself in client missions.Curiosity, passion, and a collaborative spirit.A strong interest in management and a willingness to mentor peers.Solid technical or functional skills in market finance.A degree from an engineering school or equivalent, with at least three years of experience in IT. What We Offer You:CAPFI is a vibrant company that places collective spirit and peer sharing at the heart of its culture. We provide a flexible work environment with agile project choices. CAPFI also offers:Freedom to choose your manager.Opportunities for certified training.The chance to join Tribes and foster the collective energy and expertise of CAPFI.