Freelance Backend Developers in .NET, Java, or Python

Join our innovative team at dev2 as a Senior Backend Developer specializing in AdTech. In this role, you will be responsible for designing and implementing robust backend systems that drive our advertising technology solutions. You will work closely with cross-functional teams to ensure seamless integration and performance of applications.

At Speakap, we are on a mission to revolutionize communication for frontline and deskless workers through our innovative mobile-first Employee Experience Platform. Our platform empowers over 600 clients and 400,000 users in diverse sectors such as retail, hospitality, and healthcare to stay connected, informed, and engaged directly from their smartphones, eliminating the need for traditional email and desktop communications.If you have a passion for crafting clean, scalable, and secure code and enjoy tackling challenges while bringing creative ideas to life, we invite you to join our dynamic team. Help us redefine the future of work and connectivity.What You Will DoYour main responsibility will be to develop and enhance our API, which serves as the backbone of our platform, facilitating communication between web frontends, mobile applications, and third-party services.Collaborate with cross-functional teams to implement new features and enhance existing ones.Ensure the security and performance of our services under all conditions.Engage in architectural discussions to influence technology choices and problem-solving strategies.What You’ll BringA Bachelor’s or Master’s degree along with over 5 years of experience in building scalable, high-performance, multi-tier software while adhering to SOLID principles and design patterns in an agile environment.A strong collaborative spirit, excellent problem-solving abilities, and a commitment to writing clean, maintainable code.Proficiency in PHP 8, ECMAScript 10+, TypeScript, modern frameworks (Symfony 6+ preferred), Docker, CI/CD, Git, and shell scripting.Experience with relational databases (MySQL, MariaDB), automated testing (PHPUnit, Behat), and performance monitoring with DataDog.Familiarity with AWS services (S3, SQS, Lambda, etc.), Linux environments, and network protocols; knowledge of Elasticsearch, Java (8/9), Redis, Lua, NGINX, or OAuth 2 is a plus.A passion for automation, ensuring thorough test coverage, and optimizing repetitive tasks for efficiency.What We OfferAt Speakap, we are more than just a workplace; we are a supportive team that values your growth, ideas, and well-being.

dept offers an internship for a Backend Developer in Amsterdam or Rotterdam. This position gives aspiring developers the chance to gain hands-on experience and learn from seasoned professionals. Role overview The internship centers on supporting backend development for active projects. Interns will join a team of experienced colleagues and take part in real-world software work. What you will do Assist in building and maintaining backend systems for ongoing projects Collaborate with a team of skilled professionals Share ideas and contribute code to development efforts

Are you ready to transform the banking experience? At bunq, we strive to simplify lives and redefine banking for everyone. This is your opportunity to contribute to the future of digital banking, creating the ultimate app experience. Leverage your coding skills to develop and enhance the Bank of The Free, ensuring seamless, secure, and flawless functionality for our users.Take OwnershipAs a Senior Backend Engineer at bunq, you will lead our backend development, providing users and employees with unmatched stability and performance.Collaborate with our product team to design and implement robust backend structures for innovative user-facing features, utilizing technologies such as MySQL, Redis, Elasticsearch, and PHP.Support the growth of our backend team by mentoring junior developers and helping them reach their full potential.Oversee high-availability production systems and assist other departments by developing and maintaining efficient, scalable processes.

Since its inception in 2018, Bitvavo has pioneered the digital assets trading landscape, creating a seamless bridge between traditional currencies and digital assets. Our platform is designed with transparency in mind, featuring competitive fees and an extensive range of assets, ensuring that the currency of the future is accessible to everyone.Within just two years, we have cemented our status as the leading digital asset exchange in the Netherlands and one of the largest in Europe, boasting over one million users and facilitating the exchange of tens of billions in digital assets annually.Based in Amsterdam, we are on the lookout for innovative and motivated individuals who are eager to contribute to our mission of making digital assets universally accessible.About the OpportunityWe are a dynamic and rapidly expanding engineering organization dedicated to enhancing customer access to digital assets. In response to our expanding user base and the increasing diversity of assets we offer, we're looking to grow our teams to foster innovation focused on creating and implementing advanced services within the crypto market.As we continue to evolve, we welcome experienced engineers who are passionate about making a difference. This position is continually open, and we review applications on a rolling basis. While response times may vary based on our hiring needs, we encourage you to reach out if this role aligns with your expertise. We look forward to connecting with you when a suitable opportunity arises.Your ResponsibilitiesWork collaboratively with your Engineering Manager, Staff Engineer, and fellow team members to develop high-quality software for our clients.Tackle technical challenges head-on, crafting solutions to ensure optimal performance across our systems.Engage actively in critical decisions related to technology stacks and architectural frameworks.Participate in operational rotations to address incidents within our production environment.Qualifications We SeekA minimum of 8 years of experience in software development.Deep understanding and expertise in event-driven microservices architecture, particularly with Kafka.Strong proficiency in JVM languages, especially Kotlin.Familiarity with Kubernetes and a solid grasp of design patterns and programming principles.

At PubMatic, we are revolutionizing the digital advertising landscape by empowering brands and agencies to thrive in a transparent, addressable ecosystem. We are seeking a dedicated Client Services Partner to become a pivotal member of our Advertiser Solutions team based in Amsterdam. In this hands-on role, you will be instrumental in bringing programmatic deals to fruition. Collaborating closely with agencies and brands, you will leverage data, technology, and trading expertise to optimize campaigns, foster growth, and translate performance insights into substantial outcomes across the PubMatic platform. Your Key Responsibilities Manage end-to-end post-sale campaign processes, including deal approval, activation, optimization, and renewal. Oversee deal setup, campaign launches, pacing, troubleshooting, and ongoing optimization. Conduct performance analysis and provide data-driven recommendations to enhance KPIs and revenue outcomes. Prepare weekly and monthly reports, conduct quarterly business reviews (QBRs), and analyze inventory performance. Engage in hands-on DSP trading and optimization across platforms such as DV360, TTD, Amazon DSP, or similar. Facilitate cross-functional execution in collaboration with Sales, Strategy, Addressability, Activate Trading, and Deal Desk teams. Support SPO initiatives, proposal development, and performance tracking. Drive process improvements, documentation, and operational best practices. Ideal Candidate Profile Minimum of 3 years of experience in Programmatic Trading, Client Services, or Account Management within the AdTech sector. Hands-on experience with major DSPs (DV360, TTD, Amazon DSP, or similar). Deep understanding of programmatic buying/selling, pricing models, and optimization strategies. Advanced proficiency in Excel with a strong capability for analyzing campaign performance data. Familiarity with Salesforce, Looker, Tableau, or PowerBI is preferred.

Join our innovative team at Databricks as a Senior Backend Software Engineer, where you'll contribute to cutting-edge data solutions and scalable systems. Collaborate with a talented team to design and implement robust backend services that power our platform, enabling businesses to unlock the full potential of their data.

Role overview Creative Fabrica is looking for a Senior Backend Engineer with strong Go experience to help shape the foundation of its digital platform. The focus is on building and refining scalable backend services that power a growing creative marketplace. What you will do Collaborate with a talented team to design, develop, and maintain backend systems using Go Support the reliability and efficiency of backend services as the platform expands Share ideas and technical solutions to enhance user experience and add new platform features Address challenging technical problems in backend development Location This role is based in Amsterdam, North Holland, Netherlands.

Join Our Team as a Backend Developer!At openclaims, we are pioneering the insurtech industry by providing a cutting-edge SaaS platform that streamlines car repair processes for insurers and fleets. As we expand our reach into various markets, we seek passionate individuals eager to enhance and scale our innovative product.Your Key Responsibilities:Own and optimize core backend functionalities of our platform.Collaborate with frontend developers to integrate user-facing elements.Act as a technical advisor during the development cycle, supporting various stakeholders.Design and implement workflow solutions and technical upgrades to our platform.Engage in our continuous improvement initiatives.About Your Team:Join a dynamic team of 6 developers committed to fast-paced collaboration and ownership of our projects.

Are you a passionate engineer who enjoys both establishing frameworks and engaging directly in development? As a Senior Backend Engineer at Funda, you will design, build, and scale systems that assist millions of potential home buyers and real estate professionals daily. Your role bridges technology, architecture, and product development, allowing your voice to influence our direction.Your Role at a GlanceIn this position, you will be a key player in Funda’s backend domain. Your responsibilities include designing scalable systems, enhancing the technical foundations of our platform, and developing features that make a direct difference to millions of users.You will be part of a dedicated product team while collaborating across various teams: uniting people, ideas, and projects to advance our technical capabilities. Utilizing cutting-edge technologies such as .NET 8, Kubernetes, Azure, event-driven architecture, and Terraform, you will help keep our systems intelligent, scalable, and prepared for the future.This role uniquely combines deep technical expertise, ownership, and an influential voice in our development processes.Your Responsibilities IncludeGuide your team in alignment with our lighthouse architecture and contribute to its ongoing enhancement.Design and optimize critical systems demanding high performance and reliability.Tackle complex challenges related to scalability, data streams, and systems integration.Collaborate with product managers and designers to ensure technical choices align with the product vision.Mentor and share knowledge with mid and junior engineers, fostering Funda's culture of learning.Partner with other senior and staff engineers to evolve Funda’s technical strategy.Explore our Engineering Blog: Learn how we empower our development team with modular pipelines

airapps is seeking a Backend Engineer to join the team in Amsterdam. The focus of this role is on developing and maintaining software that powers scalable applications and high-performing systems. The backend work directly supports a seamless experience for users of airapps products. Role overview Build and maintain backend systems that enable airapps products to operate smoothly Contribute to the design and architecture of software solutions built for scale Work to enhance system performance and reliability Requirements Experience developing backend applications Interest in creating scalable and efficient systems Ability to design solutions that support a strong user experience This position is located in Amsterdam.

Be Yourself at ProtolabsWe embrace diversity and are an equal opportunity employer. We encourage individuals from all backgrounds to apply, even if they don’t meet every single qualification. Your unique perspective can help us grow and innovate.Why Choose Protolabs?As leaders in digital manufacturing, we attract doers, makers, and innovative thinkers who approach their work with an entrepreneurial mindset. Our culture revolves around delivering meaningful work that introduces new products to the market at unmatched speeds. We take pride in our diverse team, which is smart, genuine, humble, and passionate. It’s our people who inspire creativity and make our workplace feel like home.Join Our Team as a Senior Backend Engineer!This position is hybrid and open to candidates located in the Netherlands.The Manufacturing Partner Marketplace is the operational backbone of the Protolabs Network. We oversee the entire order lifecycle, from matching orders to the right manufacturing partners through production and quality control to ensuring timely delivery. Our role is crucial for maintaining seamless operations and customer satisfaction.In this role, you will develop systems that drive the marketplace, including automated auctions, order allocation, supplier tools, production workflows, global logistics, quality control, and internal operations tools. We seek a pragmatic problem solver who thrives in a dynamic environment and takes ownership of both the business challenges and technical solutions.

Important: This position requires relocation to our Milan office.About SatispayAt Satispay, we are on a mission to transform daily payment experiences, making them straightforward, equitable, and accessible for everyone. Our vision extends beyond payments; we aspire to redefine the future of finance.As part of a dynamic movement, we empower millions to overcome significant challenges, fostering a culture of rapid innovation, bold thinking, and collaborative growth.If you seek more than just a job and are eager to create meaningful impact alongside a talented team, you’ve found the right place.Your RoleAs a Senior Backend Software Engineer within our Business Team, you will be instrumental in shaping the future of digital welfare payments, addressing everything from employer benefits to complex product solutions. You will ensure a seamless experience for both employers and employees, contributing to long-term satisfaction and success. Your responsibilities will include:Develop Multi-Service Solutions: Analyze and design scalable, secure, and maintainable solutions for medium-to-large projects impacting multiple services within the Employer domain, focusing on the core of welfare distribution.Maintain Technical Excellence: Implement comprehensive testing strategies that balance automation with manual testing while overseeing gradual rollouts to ensure precise and reliable welfare distributions.Proactively Resolve Blockers: Anticipate and address technical challenges, promoting knowledge sharing across teams. You will handle unique challenges related to B2B registration flows and high-volume benefit allocations, all while maintaining code quality through active reviews.Ownership and Execution: Take full ownership of your projects from inception to completion, delivering features that align with user requirements—from employer onboarding to employees utilizing their welfare benefits efficiently.

Join Databricks, a leader in data and AI, as a Backend Software Engineer. We are dedicated to empowering data teams to tackle the world’s most pressing challenges, from revolutionizing transportation to pioneering medical advancements. Our world-class data and AI infrastructure platform enables customers to leverage deep data insights for business enhancement. Founded by engineers with a customer-centric approach, we embrace every opportunity to address technical challenges, from crafting next-generation UI/UX for data interaction to scaling our services across millions of virtual machines. We are just getting started!As a Backend Software Engineer, you will collaborate with your team to develop infrastructure and products for the Databricks platform at scale.Your Impact:Our backend teams address various challenges across our vital service platforms. You may work on:Complex problems that bridge product and infrastructure, including distributed systems, large-scale service architecture, monitoring, workflow orchestration, and improving developer experience.Delivering reliable and high-performance services and client libraries for managing vast amounts of data on cloud storage solutions like AWS S3 and Azure Blob Store.Building dependable, scalable services using technologies such as Scala, Kubernetes, and data pipelines like Spark and Databricks, which power our pricing infrastructure handling millions of cluster hours daily, while developing features that empower customers to easily monitor and manage platform usage.

Join Protolabs and Be Yourself At Protolabs, we understand that women and people of color often hesitate to apply for positions unless they meet every requirement. As an equal opportunity employer, we are dedicated to fostering a diverse workplace where everyone feels valued. If you believe you might not meet every single qualification but are intrigued by this opportunity, we encourage you to apply. Your unique perspective could enhance our company!Why Choose Protolabs? As leaders in digital manufacturing, we seek proactive doers, innovative makers, and creative thinkers who approach their work with an entrepreneurial mindset. Our culture revolves around impactful work that accelerates the development of innovative products. We take pride in our diverse team, characterized by intelligence, authenticity, humility, and passion. Our people fuel our creativity and make our workplace feel like home.Exciting Opportunity: Backend Software EngineerThis role is hybrid and we welcome applications from candidates residing in the Netherlands.You will be integral to the Manufacturing Partner Marketplace, the operational core of the Protolabs Network. This encompasses managing the entire order lifecycle—from matching orders with suitable manufacturing partners, overseeing production and quality control, to ensuring timely delivery. Your contributions are vital to maintaining operational efficiency and enhancing customer satisfaction.You will develop systems that empower the marketplace, including automated auctions, order allocation, supplier tooling, production workflows, global logistics, quality control, and internal operational tools.We seek a pragmatic problem solver who thrives in a dynamic environment and takes ownership of business challenges, not just technical solutions.Our Technology Stack: Backend: Python 3.11 with FastAPI, Flask, and SQLAlchemy (including Celery with RabbitMQ for background tasks).

About UsAt Vandebron, we are revolutionizing the energy sector by prioritizing sustainability and creating a transparent platform that connects consumers directly with local green energy producers. Since our inception in 2014, we have been committed to fostering a sustainable energy future.As we enter Chapter 2 of our journey, our mission is to guarantee 100% availability of green energy - 100% of the time. We are implementing innovative solutions such as flexible wind and solar energy utilization, Smart EV Charging, and advanced energy storage systems, ensuring a proactive approach to shaping a green future.Join us in creating smart energy solutions - that’s Vandebron.The RoleWe are rethinking our technology infrastructure, and we want you to be part of this exciting transition! As a Senior Backend Engineer, you will play an essential role as we move from a Scala/ZIO foundation to a new generation of services built with Kotlin and Spring Boot. You will be instrumental in developing our future-proof platform, creating scalable and high-quality services that drive Vandebron’s mission for 100% green energy.Collaborating within a dynamic, cross-functional team of engineers, designers, and product stakeholders, you will transform complex energy challenges into efficient backend solutions. Our culture promotes knowledge sharing and experiential learning, making it an integral part of our work environment.ResponsibilitiesCollaborate with fellow engineers to design and develop new microservices utilizing Kotlin and Spring Boot.Design and uphold clean, high-performing APIs that cater to our React and React Native frontends.Produce clean, efficient, and well-documented code that meets our product specifications with increasing autonomy.Engage in all phases of the development lifecycle, including writing tests, conducting code reviews, and ensuring the delivery of high-quality software.Contribute ideas and feedback within your team to cultivate a collaborative and productive work environment.

Join bunq and be part of the transformation in the banking sector! We are dedicated to simplifying banking experiences and redefining the essence of financial services. As a Backend Engineer, you will play a pivotal role in delivering an outstanding banking application by ensuring seamless, secure, and efficient functionality for our users. Leverage your coding expertise to enhance the Bank of the Free from behind the scenes.Embrace ResponsibilityAs a Backend Engineer at bunq, you will spearhead our backend development efforts, guaranteeing our employees and users benefit from unrivaled stability and performance.Developing user-facing features.Collaborating with product teams to propose and design backend structures for new features, while supporting other departments through process development and maintenance.Utilizing technologies such as MySQL, Redis, Elasticsearch, and PHP to enhance the Bank of the Free.

Are you ready to embark on a journey where your work directly influences the housing market across the Netherlands? Join Funda as a Junior Backend .NET Engineer and contribute to a platform that helps millions of individuals find their next home. You'll gain invaluable experience from seasoned colleagues, develop real features, and witness the immediate impact of your contributions. Rather than joining just another tech firm, you'll play a vital role in enhancing the country's premier housing platform.Your Role at a GlanceImmerse yourself in the dynamic field of backend development, encompassing tasks from creating microservices to optimizing existing systems. You'll be guided by expert engineers who will challenge you to assume greater responsibilities—from your first pull request to deploying your very own features in a live environment.You will work with cutting-edge technologies such as .NET 8, Azure, and Kubernetes, learning to craft code that is not only functional but also scalable, secure, and straightforward to maintain.Your ResponsibilitiesCollaborate with your team to develop backend features for the Funda platform, which may include an API for property data retrieval or integration with mortgage information.Implement small enhancements to existing services and understand how our microservices interconnect.Create unit tests and refine your code based on peer feedback.Assess feature performance and devise strategies to enhance speed and stability.Engage in discussions regarding technical design decisions and learn how to build scalable systems.Become proficient with modern tools such as Azure DevOps, Docker, and Kubernetes.Explore Our Engineering Blog: Tom's career shift from musician to engineer at FundaYour TeamAt Funda, diverse scrum teams are dedicated to enhancing various segments of our platform—from refining the search experience to updating the systems used by real estate agents to manage their listings.We are actively seeking talent for multiple teams. Throughout the recruitment process, we will collaborate with you to identify where your skills, interests, and aspirations align best.

Note: This position requires relocation to our Milan office.About SatispaySatispay is on a mission to transform everyday payments, making them simple, fair, and accessible to everyone. As we evolve, we aim to redefine the future of financial transactions.We are a dynamic movement empowering millions, united by a common goal to tackle significant challenges. Our culture encourages rapid innovation, bold thinking, and mutual trust, with a focus on collective learning and growth.You will join our Core Team, which is vital to our infrastructure. Your responsibilities will include managing external bank interactions, orchestrating payments, and providing essential Identity and Access Management (IAM) services. Additionally, you will oversee risk management services related to credit risk and fraud detection.If you are eager to create impactful solutions that serve as the backbone for our product teams, this is the place for you.Your RoleAs a Senior Backend Software Engineer within the Core Team, you will be instrumental in developing the foundational elements of our payment platform. You will ensure the technical excellence and timely delivery of intricate systems that influence multiple services and product teams throughout the organization.Your daily responsibilities will include:Engineering Core Platform Domains: Design and refine our most critical systems, including the Transaction Ledger, IAM, and Payment Orchestration. Ensure these components are high-performing, scalable, and integrate seamlessly with our product teams.Scaling Risk & Financial Engines: Enhance and create services for bank integrations, credit risk assessments, and real-time fraud detection. Develop robust logic that safeguards our financial integrity and secures the Satispay ecosystem.Cross-Team Technical Leadership: Lead technical analyses for projects that span multiple services. Facilitate technical discussions and generate comprehensive documentation (Smart Papers) to ensure your designs are thoroughly understood by stakeholders and engineering teams.