Ruby on Rails & Node.js Application Developer (m/f)

Role Overview JobTeaser is hiring a Senior Backend Engineer with strong Ruby experience to join the team in Paris. This role focuses on building and maintaining scalable backend systems that support our platform. What You Will Do Design, develop, and maintain backend solutions using Ruby Work with cross-functional teams to deliver reliable features and impro…

About UsAt Doctolib, we are dedicated to creating scalable products that effectively serve millions of users across Europe while remaining maintainable by our talented team of developers. With multiple daily deployments and over 25,000 automated tests within our CI pipeline, our backend operates on Ruby on Rails, supported by PostgreSQL and MongoDB. Our PostgreSQL databases manage a massive 30TB of data and handle 30 million queries per minute during peak traffic.Joining the tech team at Doctolib means being part of a mission to develop innovative solutions that enhance the daily experiences of healthcare teams and patients alike. We operate in agile feature teams, collaborating closely with engineering, design, and business units.Your RoleAs the Engineering Manager, you will oversee the Core Backend Foundations team (ATP) in our Platform domain. ATP is responsible for building the foundational Ruby/Rails backend components used by all product teams, including framework elements, reusable building blocks, and ensuring security and reliability by default. Our goal is to streamline backend development for hundreds of engineers, enhancing both speed and safety.Our Platform domain prioritizes a 'Platform as a Product' philosophy, simplifying complex components so product teams can focus on accelerating their development to better serve healthcare professionals and patients. At ATP, we emphasize quality, scalability, and usability, providing essential components that uphold the highest standards of security.As an Engineering Manager, you will lead a skilled team of engineers, promote a culture of technical excellence, and shape the future of Doctolib’s backend platform. Your responsibilities will include:Guiding the team to achieve business objectives, driving individual performance and growth.Collaborating with your product partner to define the team's mission and vision, aligning on a clear roadmap for success.

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.

About VibeAt Vibe.co, we are revolutionizing the way brands connect with audiences in the streaming era. We envision that streaming TV transcends traditional brand awareness; it is poised to be the next major avenue for performance marketing. Our mission is to create the infrastructure that harnesses this $100 billion potential.As a leader in Audience First Streaming TV Advertising, Vibe.co empowers marketers to leverage TV as an effective growth channel. Our comprehensive solution integrates hyper-targeted audience segmentation, AI-driven insights, real-time campaign optimization, and incrementality measurement, providing brands of all sizes the accuracy and transparency they expect from social and search advertising, applied to the TV landscape.With over 10,000 trusted brands and a reach of more than 120 million households across 500+ apps and channels, Vibe.co consistently delivers an impressive average return on ad spend of 250% and a 20% lift in sales. Achieving a $100 million revenue run rate in less than two years, we are among the fastest software companies to reach this remarkable milestone.Our investors include notable firms such as Hedosophia (early backer of Spotify, Uber, and Airbnb), Elaia, Singular, QuantumLight, and Illusian, alongside angel investors like Carolyn Everson, board member of The Walt Disney Company and Coca-Cola. Nirav Tolia, CEO of Nextdoor, is also a member of our board of directors.Founded in 2022, Vibe.co is recognized as a pioneering platform in streaming TV advertising, merging the power of performance marketing akin to Meta and Google with the fast-evolving media landscape.About the RoleAs a key member of the Performance team, you will play a vital role in managing advertiser outcomes at Vibe. Your focus will be on bidding, pacing, and enhancing the prediction stack that drives these elements. You will report directly to Clément Schiano, Engineering Manager for Performance.This position has been created to address a clear roadmap and enhance execution capabilities, as well as to mitigate knowledge concentration challenges within the team. We seek an individual who can absorb, challenge, and expand upon existing expertise, going beyond simply delivering tickets.Three compelling reasons why a talented candidate would find this role appealing:

About UpflowUpflow is a pioneering SaaS startup specializing in advanced cash collection technology designed to help B2B companies streamline their payment processes and get paid more efficiently.Founded in 2018, we have quickly gained the trust of hundreds of businesses across the US and EMEA, partnering with notable clients such as Lattice, ProductBoard, and Instawork. Our growth has been fueled by leading investors including YCombinator, eFounders, and prominent business angels from companies like N26, Square, Mercury, Uber, and NetSuite.Join us for an exciting opportunity to work within a rapidly evolving Fintech landscape in a diverse and international setting.To learn more about our team and culture, please visit our careers page at www.upflow.io/careersAbout the RoleAs a Senior Backend Engineer, you will be part of a compact and dynamic team based in Paris or working remotely, dedicated to developing impactful features for our users. Your responsibilities will encompass a variety of areas, including integrations with third-party financial systems like ERPs and billing tools, real-time data synchronization for millions of financial transactions, and managing our REST API. We prioritize data accuracy and reliability at scale, ensuring seamless financial data exchange between systems.We embrace continuous deployment (averaging 10 deployments per day) and foster a culture of pragmatism, ownership, and a growth mindset.For insights into our engineering practices, refer to this article.Your ResponsibilitiesIn your role at Upflow, you will:Design and implement complex, high-impact features from inception to completion.Work closely with the product manager and fellow engineers to convert business needs into technical solutions.Deploy clean, maintainable code to production on a daily basis.Engage in code reviews, offering and receiving constructive feedback.Diagnose and resolve intricate data and product challenges.Optimize application performance and scalability.

Join Dailymotion as a Senior Backend Engineer and play a pivotal role in developing our core components. In this fully remote position, you will work collaboratively with cross-functional teams to design, build, and maintain scalable backend systems that power our video platform.

At Flowdesk, we are on a mission to revolutionize financial services for digital assets, establishing a global institution meticulously designed for market integrity and efficiency.In a fast-paced and continuously transforming market, we employ a disciplined, first-principles methodology that permeates every aspect of our operations. This philosophy is integral to our core services, which include institutional liquidity provision, trading solutions, OTC execution, and extensive treasury management offerings. Our dedication to clarity and efficiency allows us to craft resilient and scalable systems across our diverse business verticals.We are looking for passionate individuals who resonate with our systematic approach. Joining Flowdesk means contributing significantly to the creation of a more transparent and efficient financial market infrastructure.As a Senior Back-End Engineer at Flowdesk, you will play a pivotal role in designing and developing the foundational services that drive our global trading platform. Reporting directly to Flowdesk’s Lead of Backend Engineering and collaborating closely with the Infrastructure, Trading, and Data teams, your contributions will be vital to the scalability, performance, and reliability of our backend systems.Your collaborative mission with the backend team will encompass:Crafting, developing, and sustaining microservices primarily in Rust, with additional services and tools developed in TypeScript.Engaging in system architecture and design discussions that shape the future of our backend services and trading platform.Creating scalable and resilient backend systems to support OTC and API trading workflows.Building and optimizing high-performance trading services with an emphasis on low latency, high throughput, and fault tolerance.Designing and maintaining REST and WebSocket APIs, ensuring appropriate versioning, comprehensive documentation, and seamless integration for both internal and external clients.Writing clean, maintainable, and testable code in adherence to industry best practices, code review standards, and internal guidelines.Monitoring, diagnosing, and resolving production issues, including performance bottlenecks and service outages, in close cooperation with SRE/Infra teams.Deploying, scaling, and monitoring microservices in cloud and containerized environments, utilizing tools such as Kubernetes and modern CI/CD pipelines.

Join Fabulous Co. as a Senior Backend Engineer specializing in NodeJS and contribute to our rapid growth in the health and wellness sector. In this startup-like environment, you’ll collaborate closely with our experienced CTO to develop cutting-edge features such as marketing optimization engines and billing reports. If you’re passionate about leveraging technology to help people cultivate healthy habits worldwide, we invite you to be part of our dynamic engineering team.

Join the Voodoo TeamFounded in 2013, Voodoo is a leading technology company dedicated to creating captivating mobile games and applications with the goal of entertaining users across the globe. With a robust workforce of 800 talented individuals, we have achieved over 7 billion downloads and boast more than 200 million active users. Voodoo stands as the third largest mobile publisher worldwide by downloads, trailing only Google and Meta. Our impressive portfolio features popular titles such as Mob Control and Block Jam 3D, along with trending apps like BeReal and Wizz.Your RoleAs a Senior Backend Engineer, you will collaborate within a dynamic team of five engineers focused on enhancing our gaming backend platform. This role requires close interaction with various departments, including Core Gaming, Live Gaming, and Engineering & Data. You will contribute to our transition from Hyper-Casual to Hybrid, Casual, and Mid-Core games, playing a pivotal role in scaling our backend architecture to support new and existing titles.Your responsibilities will encompass designing scalable backend systems that serve millions of players daily. You'll partner with client developers and game designers throughout the entire process, from conceptualizing new features to their successful implementation and iteration.

Join Back Market as a Senior Backend Engineer I and be part of our mission to make refurbished devices the first choice for consumers. You will play a critical role in developing and optimizing our B2C services that enhance user experience and drive customer satisfaction. In this position, you'll collaborate with cross-functional teams to design scalable backend solutions, implement robust APIs, and ensure high performance and responsiveness of our applications.

Join us in revolutionizing the shopping experience through AI-powered conversations.At Gorgias, we are pioneering a platform that transforms customer interactions into meaningful relationships. Our vision is to create a unified AI agent that assists, sells, and re-engages customers at every touchpoint in their journey. We believe that Conversational Commerce is the future of eCommerce, and we are at the forefront of this exciting shift.Our mission is to ensure that every brand interaction is personal, seamless, and intelligent. By merging our extensive product knowledge with cutting-edge AI technology, we aim to make the shopping experience feel increasingly intuitive and connected.To achieve this, we are committed to:Quality: Crafting authentic, brand-aligned conversations.Experience: Ensuring a smooth shopping journey from chat to checkout.Re-engagement: Fostering personal dialogues instead of intrusive marketing.With the rapid evolution of AI in retail, Gorgias is laying the groundwork for the next decade of eCommerce. We envision a future where every brand has its intelligent agent, and every customer feels valued and understood.Join us in making Conversational Commerce a reality.Team & ContextGorgias is an AI-first company dedicated to developing innovative products driven by large language models (LLMs) and agent-based systems. We are the leading conversational commerce platform for Shopify merchants. Our AI Journey team is focused on enhancing the marketing aspect of our vision with AI-driven outbound conversations that engage shoppers through various channels, primarily SMS.Our product is actively utilized by merchants today, processing hundreds of millions of shopper events. We are scaling our operations to enhance AI reliability at higher volumes, broaden our shopper engagement capabilities, and solidify our systems for robust production loads. The most intriguing challenges lie ahead.This role is positioned at the nexus of product engineering and applied AI, concentrating on the development of reliable, scalable, and impactful LLM-powered experiences in production.About the RoleIn this role, you will have the opportunity to: Develop and scale production AI features utilized by thousands of merchants. Engage directly with LLMs, prompts, and agent workflows within a live product setting. Influence the architecture of AI systems as we continuously enhance our platform.

About VoodooEstablished in 2013, Voodoo is a pioneering technology company dedicated to crafting engaging mobile games and applications that aim to entertain audiences globally. With a dynamic team of 800 professionals, we boast an impressive milestone of 7 billion downloads and over 200 million active users, positioning Voodoo as the third largest mobile publisher worldwide, trailing only Google and Meta. Our diverse portfolio features hit games such as Mob Control and Block Jam, in addition to popular applications like BeReal and Wizz.Our TeamAt BeReal, we are committed to promoting authenticity in social media. By encouraging users to capture and share genuine moments, we build real connections and celebrate everyday life. Our international team, comprising over 60 members, engages more than 30 million monthly active users. With the backing of Voodoo, we are determined to scale BeReal into a leading social network that serves hundreds of millions worldwide.Your RoleAt BeReal, we have built our platform with a compact yet highly skilled technology team, and we intend to maintain this approach as we grow to accommodate hundreds of millions of users. Our commitment to speed allows us to deploy new features faster than any other established social network while we enhance our infrastructure. We operate in small, agile teams, granting each engineer significant autonomy to influence product decisions.Address thrilling technical challenges, given the unique nature of our product, which experiences user surges of millions within short timeframes.Play a vital role in developing a resilient architecture capable of accommodating massive scale as we attract new users and expand globally.Collaborate with product and engineering teams to innovate and implement new app features.Evaluate trade-offs and tackle technical challenges associated with critical backend components.Engage in code and design reviews to uphold our quality standards.Our Technology StackInfrastructure: GCP, Kubernetes, Pub/Sub, GitHub Actions, and ArgoCD.Backend: Go, Node.js (NestJS, Nx, TypeScript)Frontend: Swift (iOS), Kotlin (Android).Database: Spanner, PostgreSQL, Redis.Ideal Candidate ProfileYou possess over 5 years of experience in API development within distributed architectures.You have demonstrated expertise in Go and have a track record of developing high-volume API microservices.You are a self-motivated individual with excellent problem-solving skills and a strong desire to innovate.

Note: This position requires relocation to our Milan office.About SatispaySatispay aims to transform everyday payments by making them straightforward, equitable, and accessible to all. Our vision has expanded to redefine the future of financial transactions.We are a community empowering millions, united by a common mission to tackle significant challenges. Our approach is swift, bold, and collaborative, fostering an environment where innovation thrives and growth is continuous.As part of the Core Team, you'll engage with vital systems, overseeing interactions with banks, orchestrating payments, and offering the essential infrastructure for Identity and Access Management (IAM). The team also manages risk-related services, focusing on credit risk management and fraud detection.If you are eager to create something impactful that underpins all our product teams, you belong here.Your ResponsibilitiesIn your role as a Senior Backend Software Engineer within the Core Team, you will be pivotal in shaping the backbone of our payment platform. You will ensure the technical excellence and timely delivery of complex systems that influence various services and product teams across the organization.Your daily tasks will include:Core Platform Development: Contributing to the design and enhancement of critical systems like the Transaction Ledger, IAM, and Payment Orchestration, ensuring high performance, scalability, and functionality for seamless integration by product teams.Risk & Financial Services Optimization: Implementing and refining services for bank integrations, credit risk assessment, and real-time fraud detection, developing robust logic that safeguards our financial ecosystem.Technical Leadership: Leading technical analyses for cross-service projects, facilitating discussions, and producing comprehensive documentation (Smart Papers) to ensure clarity and robustness in your designs for stakeholders and engineering teams.

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 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.

Who We AreYubo is a dynamic social discovery platform designed for Gen Z, enabling users to make new friends and connect authentically online. By removing likes and follows, we encourage our community to express their true selves and forge real connections.With millions of active users, we are revolutionizing how young people socialize online. Our mission is to create a safe, engaging, and inclusive digital environment where everyone can feel secure and valued.Our diverse team is united by a strong commitment to fostering a safe space for our users. We prioritize safety in our operations, collaborating with technology partners and NGOs to establish leading standards in child protection.Join us on this exciting journey to redefine social interaction for the future!About This RoleAs Yubo scales, we are entering a pivotal phase of product development within our Engagement & Monetization squad. This team is dedicated to experimenting and enhancing our core business metrics.We are seeking a Senior Backend Engineer to join our Backend Experience team, reporting directly to Armand, our Engineering Manager. You will work within a multi-disciplinary squad comprising Mobile Engineers, a Product Manager, a Designer, and a Data Analyst, alongside two backend engineers to facilitate your onboarding.Your responsibility will be to set the technical direction and develop backend systems that support continuous experimentation at scale, rolling out services and business logic that cater to millions of users while ensuring reliable and safe interactions.

About Us Safran.AI, formerly known as Preligens, is a subsidiary of Safran Electronics & Defense, specializing in artificial intelligence solutions for analyzing high-resolution satellite imagery, full motion video (FMV) streams, and acoustic signals. Our innovative solutions are implemented in the aerospace, defense, and governmental sectors. Since 2016, our company has been developing sophisticated algorithms and software that automatically analyze, detect, and identify military-relevant objects from both commercial and governmental data sources. Following our integration into Safran in September 2024, Safran.AI is also playing a pivotal role in the group’s transformation by applying AI solutions to Industry 4.0 sectors. For example, automated image analysis through AI aids inspectors in identifying potential anomalies in critical components from digital images. At Safran.AI, innovation and the creation of a safer world are at the core of our mission. By joining us, you will collaborate with passionate, multidisciplinary teams (engineers, researchers, developers) among the industry's most talented professionals, all driven by a shared commitment to technological excellence. We provide a stimulating work environment where creativity and initiative are encouraged, and every idea matters. Your Mission, Should You Choose to Accept It As part of Project Robin, an innovative solution for monitoring strategic sites via satellite imagery and AI, already in production with several clients, you will join a team of 7 developers. Together, you will focus on evolving various backend modules with strong scalability and modularization challenges (data pipeline, database, API, orchestration, deployment). Note: The ability to obtain a Defense clearance is mandatory for this position. As a Senior Software Engineer, you will play a central role in bringing your technical expertise to the design, development, and implementation of our complex software solutions. Your responsibilities will include:→ Maintaining and evolving web applications (Python/FastAPI and JavaScript/React).→ Designing, developing, and maintaining our backend infrastructure and automated pipelines (Python, Airflow, PostgreSQL).→ Collaborating closely with all teams and subject matter experts to understand end-user needs.

Please note that this position requires relocation to our Milan office.About SatispaySatispay is dedicated to transforming the way everyday payments are made, striving to make transactions simple, equitable, and accessible for all. Our vision has evolved to redefine the future of finance.We are a community of innovators empowering millions, united by a common goal to address significant challenges. Our journey is just beginning. We are rapid in our actions, bold in our ideas, and foster a culture of mutual trust and continuous learning.If you seek more than just a job and wish to make a lasting impact alongside a talented team, you’ve come to the right place.Key ResponsibilitiesAs a Senior Backend Software Engineer within our Business Team, you will be instrumental in revolutionizing digital welfare payments - managing everything from employer benefits to intricate product solutions. You will enhance the complete experience for both employers and employees, ensuring sustained satisfaction. Your role will encompass technical leadership, quality assurance, and the delivery of complex systems that enable thousands of employers to effectively manage their corporate welfare solutions. Here’s what your typical day will include:Design Multi-Service Solutions: Undertake technical assessments for medium to large-scale projects impacting various services in the Employer domain. You will architect robust, highly-available solutions with a focus on scalability, security, and maintainability that are core to our welfare products.Maintain Technical Quality: Implement comprehensive testing strategies that balance automation and manual efforts, overseeing gradual rollouts with meticulous monitoring to ensure that welfare distributions remain accurate and dependable.Proactively Resolve Challenges: Anticipate and address technical obstacles, fostering knowledge sharing across the organization. You will navigate the unique complexities of B2B registration processes and high-volume benefit distributions while ensuring code quality through diligent reviews.Ownership and Execution: Take full ownership of your projects from inception to completion, delivering functionalities that genuinely cater to user requirements - from the moment an employer registers to the moment an employee utilizes their welfare benefits through seamless backend integration.

About the Role Shift Technology is looking for a Junior Backend Engineer with C# experience to join the team in Paris, France. This role focuses on building and maintaining backend systems that power the company's products. Work closely with seasoned engineers and contribute to projects that shape Shift Technology's technical direction. What You Will Do Develop and support backend components using C# Help maintain and improve existing systems Collaborate with other engineers on technical projects Location Based in Paris, France.