Mid/Senior Back End Engineer - Ruby

Netguru is a Certified B Corporation® that builds software for entrepreneurs and innovators. The team values trust, ownership, and transparency, working to create a safe and inclusive environment where everyone can be productive. Feedback is encouraged, and the company continually looks for ways to improve. Freelancers at Netguru set their own schedules and choose where and how they work. Assignments are matched to individual strengths, offering experience with projects from a range of industries. Freelancers can also explore full-time collaboration and become part of the wider team culture. Learn more about freelancing at Netguru: https://www.netguru.com/blog/who-are-netguru-freelancers Role overview This freelance position is for a Senior Ruby on Rails Developer. The role requires strong Ruby on Rails expertise, comfort with JavaScript, and familiarity with email delivery tools such as Mailgun or SparkPost. Requirements Extensive experience with Ruby on Rails Solid background in JavaScript Familiarity with email delivery tools (Mailgun, SparkPost, or similar) What Netguru offers Fully remote work (Poland-based, CET time zone +1/-1) Flexible hours and work locations Developer-friendly processes Potential for long-term collaboration Contract details Freelance, B2B contract Full-time assignment for 6 months

Code & Pepper works with clients in FinTech, HealthTech, and AI, taking on projects that demand accuracy and dependable results. The team assists organizations in scaling their operations, refining platforms, and launching new features when deadlines are tight. Role overview The Senior Fullstack Developer (Ruby / React) will contribute to a SaaS platform designed to improve pharmacy operations. This platform addresses everyday challenges such as long customer lines, repeated phone inquiries, manual administrative work, and prescriptions left uncollected. What you will work on Enhancing features that allow pharmacies to process online payments and send automated prescription reminders Building tools that help pharmacies connect with patients more effectively Supporting the platform’s goal of increasing pharmacy sales through a unified, user-friendly application Location This is a remote position (praca zdalna).

Join airSlate as a Fullstack Developer!At airSlate, we are at the forefront of innovation in SaaS technology, specializing in no-code workflow automation, electronic signature, and document management solutions. Our award-winning suite of products, including SignNow, pdfFiller, DocHub, airSlate WorkFlow, Instapage, and US Legal Forms, empowers hundreds of millions of users and over one million clients globally. We help organizations of all sizes digitize processes, enhance efficiency, and revolutionize their operational methodologies.We’re experiencing a thrilling phase of growth, with talented team members spread across more than 20 countries on three continents, prominently including the United States, Poland, Romania, Ukraine, and the Philippines. At airSlate, we cultivate a culture of value creation for our customers and a collaborative environment fostering growth and innovation.About DocHubOur ambitious DocHub team of 20+ technologists is dedicated to perfecting our Google-integrated PDF editing and signing solution. DocHub simplifies the processes of document editing, signing, distribution, and form completion, allowing users to seamlessly import, export, modify, and sign documents directly from Google apps, ensuring streamlined business operations and dynamic workflows.We are on the lookout for a talented Fullstack Developer (Ruby) who is ready to contribute to the exciting next chapter of our journey!

Join a dynamic team at Quorso as a Full-Stack Developer! Founded in 2016, Quorso is revolutionizing retail management with its innovative SaaS solutions. Our Agile Stores technology transforms vast amounts of retail data into actionable insights for store managers, enhancing operational efficiency and sales performance.As a Full-Stack Developer, you will play a crucial role in expanding our platform's capabilities. You'll be involved in creating data transformation pipelines and enhancing our core application, which includes developing APIs, user interfaces, and the underlying infrastructure for core insights.Your Role:You will collaborate with a talented team of engineers to introduce new functionalities into our platform. This role presents an exciting opportunity to contribute to a system that could evolve into a comprehensive task management tool for users and managers alike.Key Responsibilities:Engage in solving business challenges by designing effective user workflows.Contribute to technical design discussions for project scope.Provide constructive feedback during visual design review sessions.Assist in detailed technical implementation planning.Develop features end-to-end, encompassing both backend and frontend using Ruby on Rails, React, and Redux frameworks, with a balanced focus on both (50/50).Essential Qualifications:Proven experience in proactive problem-solving and technical implementation planning.Background in providing feedback for visual designs and working collaboratively in technical environments.Hands-on experience with Ruby on Rails, React, and Redux is essential.

Flying Bisons is a premier Digital Consulting and Delivery company situated in the vibrant city of Warsaw, Poland. Our mission is to empower our clients to Unleash Digital Potential™. We excel in discovering, defining, designing, and developing top-tier digital products that yield impactful business results for our clients, creating outstanding digital experiences for millions worldwide.What sets us apart is our comprehensive end-to-end process that equips us to tackle every challenge with the assurance of achieving optimal results. Our areas of expertise encompass Research, Digital Strategy, Branding, Content Creation (Written, Photos, Videos), Product Design, Web & Mobile Development, Data Analytics, and AI.Become part of our dynamic team of 120 professionals and collaborate in crafting groundbreaking products and exhilarating experiences for notable brands(such as Mercedes AMG, IKEA, KFC, eObuwie, Żabka, Sanofi, Zain) and innovative startups (like Booksy, Nethone, Telemedi, or DevSkiller)!We are in the process of building a curated network of talented freelance Backend Developers to engage for both current and future projects. When you apply to join our freelancer base, your application will be assessed and kept on file. You may not be contacted immediately, but once a project aligns with your expertise, you will receive an invitation to participate, allowing you to accept or decline based on your availability. If you're interested in joining our talent pool, please submit your CV. We will reach out as soon as a fitting opportunity becomes available.Are you a self-motivated and reliable professional? If so, we are eager to hear from you!

Join our dynamic team at Sigma Software Group as a Principal Software Engineer specializing in Ruby. In this role, you will lead innovative projects, drive technical excellence, and mentor junior developers. Your expertise will be pivotal in shaping our software solutions and enhancing our development practices.

Join Netguru, a leader in the digital commerce landscape, as we partner with renowned brands to elevate their B2B solutions, marketplaces, and retail ecosystems. Since our inception in 2008, we have empowered businesses with state-of-the-art technology, AI-driven personalization, and top-notch engineering and design teams. As a certified B Corporation®, we take pride in our collaborations with major brands such as IKEA, VW, OLX, Delivery Hero, Żabka, Wolt, Careem, and Vinted.How does freelancing work at Netguru?As a freelancer at Netguru, you have the flexibility to choose your working hours, location, and project tasks. We align your skills with suitable projects, providing you access to diverse opportunities across various industries. This not only enhances your experience but also allows you to broaden your skill set.Moreover, Netguru freelancers can engage in full-time collaborations, truly becoming integral members of our team. Are you ready to make a significant impact? Join us, and let’s create stunning software together.Currently, we are seeking a Senior Frontend Developer to join our team.

Hello We are Bïrch, a transformative platform designed for creative and growth marketing teams, encompassing content creation, collaboration, and ad campaigns all in one powerful toolbox. With over 9 years in the business, we proudly serve more than 800 companies and 5,500 marketers. Our platform has facilitated billions in ad spend, positioning us as one of Meta's fastest-growing partners, officially endorsed by both Meta and Google. Following our rebranding from Revealbot to Bïrch, we have documented our transformative journey here.As we transition from a single successful product to a multi-product platform, we launched Bïrch Hub last year in collaboration with Meta, a user-friendly server-side tracking tool for ads. To support our ongoing growth, we are expanding our backend team. In this position, you will not only maintain existing systems but also play a pivotal role in developing new products and services, shaping architecture collaboratively, and making significant technical decisions by writing high-quality code across our dual-language backend using Ruby on Rails and Go. About UsWe are a remote-first team of friends scattered across the globe, with our headquarters located in Barcelona. Having already established a successful product, we are now embarking on a broader vision. We hire talent worldwide and cherish our offline meetups: in the last two years, we gathered in Barcelona, and previously, in Istanbul. Check out our team’s Instagram to learn more about our diverse cultures and backgrounds.

Kronospan is looking for a Rail Freight Operator based in Szczecin. This role is central to the company’s rail logistics, helping shipments stay on track and supporting the broader transportation network. Key responsibilities Oversee day-to-day rail transportation logistics Coordinate the movement of goods by rail to meet schedules Monitor shipments to support timely and efficient delivery Contribute to reliable supply chain operations and uphold service standards This position helps ensure that goods move smoothly through the supply chain, maintaining the steady flow required for Kronospan’s operations.

Join Netguru, a pioneering force in digital commerce, as we assist renowned brands in modernizing their B2B solutions, marketplaces, and retail ecosystems. Since our inception in 2008, we have empowered businesses through innovative technology, AI-driven personalization, and exceptional engineering and design teams. As a certified B Corporation®, we proudly serve major brands such as IKEA, VW, OLX, Delivery Hero, Żabka, Wolt, Careem, and Vinted.We are currently seeking a Senior Backend Engineer with robust architectural expertise to engage in a long-term project for a European client in the laboratory and biotech sector. This position is a single-developer project, requiring close collaboration with the client’s internal teams and laboratory stakeholders to clarify requirements, outline the project scope, and enhance existing backend processes. Strong communication skills are vital, as you will frequently participate in technical discussions with LIMS and laboratory teams. Your role will encompass hands-on development, legacy code refactoring, and contributing to a scalable, well-structured backend architecture. Please note that candidates must be based in the EU due to client stipulations.Position: Senior Backend Engineer (Java / Architecture)Contract: Freelance / B2B – Remote (EU Only)Rate: 36–50 EUR/hourLanguage: English C1Key ResponsibilitiesOperate independently as the sole backend engineer on the project.Refactor and modernize legacy backend systems.Enhance and expand existing microservices and backend integrations.Maintain and develop REST and SOAP interfaces.Engage with laboratory teams and LIMS stakeholders to define requirements.Guarantee stable operation of backend services in an on-premise Kubernetes environment.Work collaboratively with internal client teams to ensure architectural consistency.QualificationsTechnical Skills & ExperienceExtensive experience with Java (Spring / Spring Boot).Strong architectural and problem-solving abilities.Proficient in designing and maintaining REST APIs.Familiarity with SOAP services.Experience in microservices environments.Hands-on experience with Kubernetes (preferably on-premise setups).Background in working with or integrating LIMS systems.Solid understanding of refactoring and modernizing legacy code.Excellent communication skills for direct collaboration with laboratory stakeholders.Proficiency in English at C1 level.Must be based in the European Union.BenefitsIn return, we offer:100% remote, flexible work environment;Access to cutting-edge technology and tools;Opportunities for professional development.

Join Netguru, a leading partner in digital commerce, as we empower top brands to innovate their B2B solutions, marketplaces, and retail ecosystems. Since our inception in 2008, we have been at the forefront of technology, utilizing AI-powered personalization and delivering exceptional engineering and design services. As a certified B Corporation®, we are proud to partner with industry giants such as IKEA, VW, OLX, Delivery Hero, Żabka, Wolt, Careem, and Vinted.What does freelancing look like at Netguru?As a Netguru freelancer, you have the flexibility to define your work style. Choose your working hours, location, and project types that align with your expertise.We ensure that you are paired with projects that match your skills, offering diverse opportunities across various industries. This approach not only enhances your experience but also allows for skill diversification.Moreover, our freelancers can engage in full-time collaborations, becoming integral members of our teams.If you are ready to make a significant impact, join Netguru, and let’s create remarkable software together.We are currently seeking AI-savvy Mid and Junior Python Developers to contribute to our client’s projects.Details:Freelance assignmentFull-time commitmentB2B contractStart date: ASAPDuration: 8-12 months (with a possibility of extension)Working hours: 9 AM - 5 PM CETSalary for Junior: up to 24 EUR/hourSalary for Mid: up to 34 EUR/hourYou will have the opportunity to work on one of three impactful projects for our client:Project #1: Develop a universal health profile for users and their families, transforming fragmented records into insightful products that promote longer, healthier lives.Project #2: Address the doctor capacity crisis by enhancing doctors' ability to manage 30% more patients without compromising quality or risking burnout.Project #3: Create a marketplace that serves as the primary access point for healthcare services across various channels.

Join Netguru, a reputable leader in digital commerce, as we partner with prominent brands to revolutionize B2B solutions, marketplaces, and retail ecosystems. Since our inception in 2008, we have empowered businesses with innovative technology, AI-driven personalization, and exceptional engineering and design expertise. Proudly certified as a B Corporation®, we are trusted by industry giants including IKEA, VW, OLX, Delivery Hero, Żabka, Wolt, Careem, and Vinted.Freelancing at Netguru:As a Netguru freelancer, you have the unique opportunity to tailor your work environment. You will determine when, where, and how you engage with projects and tasks. Our team ensures that your assignments align with your skills and interests, providing you with diverse opportunities across various industries to enhance your experience and skill set.Moreover, as a Netguru freelancer, you are not just an outsider; you become an integral part of our team with the possibility of full-time collaboration.Are you ready to make a significant impact? Come aboard Netguru, and let’s create exceptional software together.We are currently looking for a skilled Senior Golang Developer.This role is a freelance position on a B2B contract, focusing on the development and scaling of distributed systems and services. The position is 100% remote and requires the selected candidate to be available to start as soon as possible.B2B Contract | Up to 39 EUR/h | Remote | Immediate Start

Join Valtech, a leading experience innovation company and trusted partner to some of the world's most recognized brands. We offer our team members numerous growth opportunities, a values-driven culture, and the chance to shape the future of customer experiences.The OpportunityAs a Senior Salesforce Marketing Cloud Developer at Valtech, you will engage in an environment focused on continuous learning, impactful contributions, and professional advancement. Your role will involve pioneering new digital solutions and reimagining customer experiences, ultimately driving transformation across various industries.

Flying Bisons is a premier Digital Consulting and Delivery firm located in the vibrant city of Warsaw, Poland. Our mission is to empower our clients to Unleash Digital Potential™. We specialize in discovering, defining, designing, and developing top-tier digital products that yield significant business outcomes, crafting digital experiences for millions globally.What sets us apart is our comprehensive end-to-end process, enabling us to tackle every challenge with the assurance that we deliver exceptional results. Our expertise spans Research, Digital Strategy, Branding, Content Creation (including Written, Photography, and Video), Product Design, Web and Mobile Development, Data Analytics, and Artificial Intelligence.Become a part of our dynamic team of 120 professionals as we co-create industry-defining products and exhilarating experiences for renowned brands(Mercedes AMG, IKEA, KFC, eObuwie, Żabka, Sanofi, Zain) and innovative startups(such as Booksy, Nethone, Telemedi, and DevSkiller).We are assembling a curated network of skilled freelance React Native Developers to collaborate on current and forthcoming projects. By applying to join our freelancer pool, you will undergo an evaluation process and remain in our records for future opportunities. While you may not be contacted immediately, when a project aligned with your expertise arises, you will be invited to participate, with the option to accept or decline based on your availability. If you are enthusiastic about joining our talented pool, please submit your CV. We will reach out once a fitting opportunity emerges.Are you a self-motivated and reliable professional? If so, we eagerly await your response!Contract type: B2B

About UsAt Ruby Labs, we are at the forefront of technological innovation, crafting and managing groundbreaking consumer products across various sectors, including health, education, and entertainment. Our dynamic teams are dedicated to shaping the future of consumer-oriented solutions, and we are constantly on the lookout for passionate individuals to enhance our mission. Discover more about our journey at https://rubylabs.com/about-us/.About the RoleWe are seeking an adept Middle Golang Developer to join our team. In this role, you will take charge of developing scalable, high-performance backend services and will play a key role in enhancing our billing system. As part of a cross-functional team comprising engineers and product managers, your work will focus on delivering consistent, sustainable results. We value individuals who are enthusiastic about innovation, eager to stay updated with emerging technologies, and possess exceptional communication and collaboration skills, especially in a remote setting.Key ResponsibilitiesSoftware Development: Engage in the development and maintenance of robust backend services and applications utilizing Golang.Microservices Architecture: Design, implement, and optimize microservices-based applications, ensuring they are scalable, reliable, and maintainable.Container Orchestration: Work in conjunction with the DevOps team to deploy and manage Golang applications within Kubernetes clusters, utilizing Helm for efficient package management.Database Management: Design and refine database schemas, queries, and transactions with a focus on Postgres, ensuring data integrity and performance. Use Redis to enhance application efficiency.Billing System: Develop and improve the billing system to guarantee accurate and timely processing of financial transactions.Code Review: Perform code reviews to uphold code quality, best practices, and compliance with coding standards.Collaboration: Work collaboratively with the cross-functional team, including DevOps, backend and frontend developers, QA, and product management, to grasp requirements and deliver high-quality software solutions. Maintain comprehensive documentation for code, architecture, and processes to ensure effective knowledge transfer.

At Valtech, we are an experience innovation company, recognized as a trusted partner to some of the world’s most esteemed brands. We are committed to providing our team with ample growth opportunities, a values-driven culture, and international career prospects that empower you to shape the future of experience.The OpportunityJoin us at Valtech, where an environment fostering continuous learning, meaningful impact, and professional growth awaits you. As a Senior Salesforce Engineer, you will be at the forefront of pioneering new digital solutions, challenging conventional thinking, and building the next generation of customer experiences.

Fraud Alert: Please be aware that scammers frequently post fake job listings. To ensure your application is valid, only apply for roles directly through the Sensor Tower official website or through reputable job platforms like LinkedIn, Indeed, BuiltIn, or Hackajob. Sensor Tower will never request payment or financial information during the application process. Communication from Sensor Tower will only come from email addresses ending in sensortower.com. All interviews will be conducted via phone or Zoom, and we will not shift communication to any external email or text message. If you encounter any issues, please let us know. Remember to attach your resume when applying.To Recruitment Agencies: Sensor Tower does not accept unsolicited resumes. Please refrain from sending resumes to our job alias, employees, or other locations. Sensor Tower is not liable for any fees related to unsolicited applications, and we will not pay any third-party agencies without a signed agreement.About the Role: We are seeking skilled engineers who can effectively scale our database operations, handling vast amounts of data (in the range of tens of terabytes) while providing meaningful insights. As a Back End Engineer at Sensor Tower, you will contribute to building exceptional products and features for our users. In our dynamic and flat organizational structure, you will have a significant influence on product development.A Day in the Life:Interviewee: Engineering Team Lead - Sasha YelkovenkaWhat does your day-to-day look like as a Software Engineer?I handle a considerable volume of data that is constantly growing. My primary responsibility is to ensure our customers can access this data swiftly and utilize convenient tools for consumption. I appreciate the culture of ownership and accountability in my work.How do you collaborate as a remote employee?Sensor Tower fosters an excellent remote working atmosphere. We frequently collaborate via Zoom to leverage our collective expertise for superior results.

Netguru is a pioneering partner in the realm of digital commerce, dedicated to assisting renowned brands in the modernization of B2B solutions, marketplaces, and retail ecosystems. Since 2008, we have empowered businesses through innovative technology, AI-driven personalization, and exceptional engineering and design teams. As a certified B Corporation®, we have built a reputation as a trusted partner for major brands such as IKEA, VW, OLX, Delivery Hero, Żabka, Wolt, Careem, and Vinted.Freelancing at Netguru: Your Flexible PathAt Netguru, our freelancers enjoy the liberty to choose their projects, working conditions, and schedules. We align you with opportunities that suit your expertise, allowing you to gain diverse experiences and develop new skills across various industries. Not only can you work on exciting projects, but you can also engage in full-time collaborations, becoming a valued member of our team.Are you ready to leave your mark? Join Netguru, and together we can create remarkable software.We are currently seeking a Senior Fullstack Engineer with proven experience in implementing Instagram Login independently.Compensation: up to 160 PLN/h (on a B2B contract)Engagement Level: Full-timeWorking Hours: CETStart Date: 31.01.2026Project Duration: 2 monthsKey Responsibilities:Overseeing the 'App Review' Process: Managing the complete verification cycle with Meta, including creating necessary screencasts and writing scope justifications to ensure app approval for Live access.Setting Up Meta Ecosystem: Correctly configuring the application environment in the Meta for Developers console, identified as a primary risk area by the client.OAuth Strategy & Implementation: Implementing the 'Login with Instagram' flow to securely retrieve specific influencer data points for profiling.Providing Technical Guidance: Serving as the subject-matter expert to navigate Meta's stringent policies and mitigate application rejection risks.Required Qualifications:Fluency in Polish and English.Experience with OAuth 2.0.Familiarity with Instagram Graph API.Experience with Meta App Review.Preferred Skills:Knowledge of Passport.js / NextAuth.js / OmniAuth (based on tech stack).Understanding of JWT (JSON Web Tokens).Experience with OpenID Connect (OIDC).Familiarity with Facebook Login Kit.Basic knowledge of GDPR compliance.Perks:What We Offer You:100% remote work flexibility.

Are you a Kotlin aficionado ready to influence the future of artificial intelligence? As large-scale language models transform from basic chatbots to advanced developer assistants capable of reasoning through complex software systems, your coding prowess will play a crucial role in shaping this evolution. By providing high-quality engineering data, you'll enable tomorrow's AI to assist developers in tackling real-world challenges with greater speed and precision. We are seeking Kotlin specialists who can translate real-world engineering scenarios—such as bug reports or feature requests from a Git repository—into clean, efficient, and idiomatic Kotlin solutions. Your contributions will involve crafting high-quality code patches that adhere to contemporary Android development standards, ensuring technical correctness, maintainability, and clarity. The ideal candidate will possess hands-on experience with modern Android and Kotlin development, including tools such as Jetpack Compose, Kotlin Coroutines, and libraries like Room, WorkManager, Datastore, ViewModel, and Hilt. A solid understanding of build.gradle configuration, dependency management, and networking libraries like OkHttp, Retrofit, and Coil is essential. Experience with Android multimedia tools (CameraX, ExoPlayer, Media3) is a valuable plus. On a typical day, your responsibilities will include evaluating AI-generated code, rectifying errors, implementing optimized Kotlin solutions, and documenting best practices that exemplify modern Android design patterns and coding conventions. A robust background in Android software development is a prerequisite, with demonstrable experience in building and maintaining production-level Kotlin applications. Excellent communication skills and the ability to articulate technical decisions are critical for success in this role. We offer a competitive pay rate starting at $35 per hour, with the exact amount determined based on your experience, expertise, and geographical location. Please note that as a contractor, you will need to provide a secure computer and high-speed internet; company-sponsored benefits such as health insurance and PTO do not apply.