Junior Backend Engineer - C#

About UsAt Harmattan AI, we are pioneering the development of autonomous and scalable defense systems. With a recent $200 million Series B funding round that has raised our valuation to $1.4 billion, we are poised for growth and are seeking talented individuals to join our mission of delivering cutting-edge systems to allied forces.Our guiding principles are centered around creating impactful technologies, striving for excellence, setting ambitious objectives, and confronting complex technical challenges head-on. We thrive in a dynamic environment where accountability, precision, and execution are critical.About the RoleWe invite a passionate Backend Software Engineer to become a vital part of our C2 Core team in Paris. In this role, you will be instrumental in developing the foundational architecture for our advanced tactical Command and Control (C2) application. You will operate in a high-stakes, technical environment where low latency, high availability, and secure data management are crucial.Your primary responsibilities will involve ensuring seamless data flow for real-time telemetry, high-bandwidth video streams, and mission commands between our fleet of robots and the internal C2 components, including the Common Operational Picture (COP) and Mission Planner. This system is designed for deployment on ruggedized tactical PCs in field environments often characterized by limited network connectivity.

About UsAt Harmattan AI, we are pioneering the creation of autonomous and scalable defense systems that cater to the needs of modern warfare. Following a successful $200M Series B funding round, our valuation has surged to $1.4 billion, prompting an expansion of our talented teams to deliver mission-critical solutions for allied forces.Our mission is driven by core values: developing technologies that create a tangible impact, striving for excellence in our pursuits, setting ambitious objectives, and tackling challenging technical hurdles. We thrive in a demanding environment where rigor, ownership, and execution are paramount.About the RoleWe are in search of a talented Front-End Engineer to become a vital member of our C2 Core team based in Paris. This role involves crafting the operator's interface for our tactical Command and Control (C2) system, focusing on the Human-Machine Interface (HMI) that connects operators with the battlefield.The context you'll be working in emphasizes the significance of managing cognitive load alongside software performance. The user interface you design will be operational on tactical PCs in the field, demanding real-time updates for the Common Operational Picture (COP), the ability to render multiple live video streams, and an intuitive interface for mission planning and fleet command.Key ResponsibilitiesCOP Visualization: Develop interactive maps and 2D/3D geospatial overlays to visualize real-time robot telemetry, sensor data, and mission routes.Real-Time Video Grid: Build a low-latency, robust video player interface capable of managing multiple streams without freezing the main UI thread.Mission Planning & Command: Create interactive tools enabling operators to establish waypoints, configure mission parameters, and issue real-time commands to the fleet.Performance Architecture: Design a state management system that can efficiently handle high-frequency data from the backend bus while preventing UI jitter or memory leaks.Collaborative Development: Collaborate closely with UX/UI designers, backend engineers, and mission planning algorithm developers to streamline workflows and minimize the number of clicks for operators.Optimization: Ensure the UI meets strict performance benchmarks, including consistent 60fps rendering, even during high-frequency map updates.

Join Mistral as a Backend Software Engineer and be part of a dynamic team that is shaping the future of cloud technology. In this role, you will be responsible for developing robust backend systems, ensuring seamless integration, and optimizing performance. Collaborate with cross-functional teams to deliver innovative solutions that meet our clients' needs.

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:

Join the dynamic technical teams at iad Business Factory, where you will work under the guidance of an Engineering Manager. You will be part of a collaborative squad consisting of developers, Product Owners, Project Managers, Quality Assurance specialists, and designers, all focused on enhancing our Playiad application.Your role will involve developing innovative web-oriented projects as well as evolving and maintaining existing features in a continuous improvement mindset.You will be integrated into the Grow Squad within the MLM Tribe, responsible for core MLM model developments including sponsorship, onboarding, accreditation, real estate training, organizational dynamization (gamification), and genealogical evolution across various geographies. Your primary responsibilities will include:Developing based on concepts established by the technical management (Clean Architecture, TDD, DDD, BDD, etc.),Understanding the business needs of each user story (product culture),Ensuring high quality in deliverables through test-driven development,Engaging in self-directed learning and staying updated on technologies and best practices,Adopting a straightforward and pragmatic approach to development,Collaborating closely with your product family members,Ensuring the reliable operation of applications in production ("You build it, you run it"),Adhering to software craftsmanship principles and XP practices. Technical stack:Development: PHP, SymfonyDatabases: PostgreSQL, MySQLInfrastructure as Code: Terraform, AnsibleAWS: EC2/ECS, RDS/Aurora, Lambda/Step Functions, API GatewayCommunication systems: RabbitMQ, AWS SQS, SNSLinux environment, Shell scripting, Cron jobs, etc.CI/CD tools: GitHub, Docker, GitHub Actions, Jira, Confluence

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.

Join us as our inaugural Software Engineer for User Safety Tooling at amo!About the PositionAs a pivotal member of our User Safety team, you will architect and implement systems designed to safeguard our users, facilitate data collection, and ensure adherence to global regulations. You will become part of a dynamic and agile team that encourages creativity and innovation in developing impactful safety tools.At amo, we are dedicated to creating social applications that connect friends, and prioritizing user safety is integral to our mission. Collaborating with our User Safety lead, you will help construct the foundational infrastructure that keeps our community secure.Your ResponsibilitiesDesign and develop highly scalable, efficient, and resilient trust and safety platforms and tools, including data tracking pipelines.Enhance systems for improved data collection, compliance, and safety procedures.Develop APIs and integrate with third-party services.Create intelligent workflows to automate complex decision-making processes.Align product objectives with user-friendly platform development that meets operational requirements.Ensure uninterrupted safety services that can scale with our growing user base.About YouRequired QualificationsMinimum of 5 years experience in trust and safety tooling or content moderation systems.Strong proficiency in designing data structures, developing algorithms, and expertise in at least one programming language (Go, Kotlin, C, or C++).Excellent communication skills and a collaborative mindset.A demonstrated passion for user safety, human and AI moderation, and operational efficacy.Preferred QualificationsExperience with web development and frontend technologies.Familiarity with online safety regulatory requirements (DSA, etc.).Experience with machine learning models and data pipelines.Life at amoWe believe in setting our team up for success through collaboration, which is why we work together onsite five days a week.

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 the Innovators at AragoArago is a pioneering company at the forefront of artificial intelligence and semiconductor technology, dedicated to advancing the future through groundbreaking innovations.Established in 2024 by a team of visionary AI researchers and physicists, Arago harnesses expertise in photonics, electronics, software, mathematics, and machine learning. Our nimble team consists of talented engineers and scientists from leading global institutions.With a multicultural team representing nine nationalities, we operate from key hubs in France, North America, and Israel. We are passionate about exceptional science and rapid progress, guided by principles that define our culture:Deliver Excellence: We take pride in our work, ensuring it meets the highest standards.Speed of Execution: We value quick, decisive actions, progressing efficiently to achieve our goals.Collaborative Spirit: We work as one cohesive unit, fostering relationships built on trust and respect.Supported by leaders from major tech companies such as Apple, Arm, Nvidia, Microsoft, and Hugging Face, along with esteemed venture firms, Arago is poised to redefine the future of technology.

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.

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.

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.

Join Contentsquare as a Software Engineer focused on streaming and data-intensive systems. In this role, you will design and implement high-performance solutions that handle large data flows, ensuring scalability and reliability. Collaborate with cross-functional teams to drive innovation and enhance our data processing capabilities.

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.

BlaBlaCar’s Carpool Supply team in Paris works on the systems at the heart of the company’s carpooling platform. As a Backend Engineer here, the work shapes how people arrange and share rides, influencing the experience for both drivers and passengers. Role overview This position centers on developing and refining backend services that support carpooling features. The team’s efforts help ensure the platform remains reliable and easy to use as it grows. What you will do Design, build, and maintain backend services for carpooling Create solutions aimed at improving the experience for drivers and passengers Work closely with engineers and product teams to deliver systems that scale and perform reliably Location This role is based in Paris, France.

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!

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.

Back Market is looking for a Senior Software Engineer focused on Order Management Systems to join the team in Paris. This position centers on developing and refining the platform to support a smooth experience for customers as they place and manage orders. Role overview This engineer will play a key part in building and maintaining scalable software solutions for order management. The work involves collaborating with colleagues from different departments to design, implement, and support features that improve how orders are handled across the platform. What you will do Contribute to the development and optimization of the order management platform Work with cross-functional teams to create and maintain scalable solutions Help ensure a seamless experience for customers managing orders Drive improvements and support ongoing innovation in order management processes Requirements Experience in software engineering, particularly with order management systems Ability to design, implement, and maintain scalable software Strong collaboration skills to work with multiple teams

About the Role airapps is looking for a Backend QA Engineer in Paris to help keep our backend systems reliable and high quality. This role works closely with engineers and product managers to improve how we build and test software. What You Will Do Develop and maintain testing frameworks for backend applications Create automated tests to catch issues early and ensure smooth releases Collaborate with team members to refine development and QA processes Help uphold quality standards so our applications meet user needs Location This position is based in Paris.