15 backend engineer jobs found

Overview Models write backend code that passes the happy-path test and falls over on everything else: the race condition under load, the N+1 that melts the database, the API contract that breaks every client the day you change it. Someone has to reason about the system, not just the snippet, and that someone is you. As a Backend Engineer you'll stress-test how models design services, data models, and APIs, expose where their reasoning breaks under real load, and write the answers a strong backend engineer would stand behind. What you’ll actually do Probe backend reasoning across service design, data modeling, and API contracts, and see where the model's design falls apart. Find the failures that matter : race conditions, N+1 queries, bad indexes, and breaking changes hiding in a clean-looking diff. Write the correct design when the model falls short, with the scaling and consistency trade-offs made explicit. Roles this fits Common backgrounds:...

(Freelance) Senior Backend Engineer (m/f/d) - Agent SDK Why voize? Because we're more than just a job! At voize, we believe the greatest gift to frontline workers is time - time to care, connect, and be present. Today, that time is lost to busywork and complex systems that pull them away from what matters most: people . Our vision is to change that by building AI companions that seamlessly take over digital workflows. We don't replace humans with technology - we amplify their impact. Our mission is backed with a $50M Series A funding led by Balderton Capital , with support from HV Capital, Y Combinator and other leading VCs. Today, 2,000+ facilities trust voize, and over 200,000 users rely on our AI companion to ease their daily workload. As a dynamic team, we combine first-in-class technology with meaningful social impact. And now, we're looking for you to join us on this mission! Your Mission: Build the layer every agent...

Fully remote, outside IR35 contract role until 31/05/2027 - up to £750 per day Reapit - Who are we? Reapit is the original end-to-end business technology provider for estate agencies of all sizes. We've been helping sales and lettings agents build relationships and grow their businesses for more than 25 years. Our technology empowers property professionals across Europe, the Middle East, Australia, and New Zealand to work with buyers, sellers, tenants, and landlords to deliver a dream home experience. Worldwide, over 100,000 agents across more than 15,000 branches use Reapit to run their businesses, manage properties, collect rent, engage clients, and provide outstanding customer service every time. What you'll be doing Reporting to the Director of Engineering, you'll operate as a highly senior, technically hands-on Back End engineer, Embedded into a squad and owning delivery of substantive, cloud-native services end-to-end. Ad-hoc client...

Android Developer (Contract, Outside IR35) Contract status: Outside IR35 Start date: 2nd November Contract length: To the end of December 2026, with extension possible Location: Remote first London days: Once or twice a month Who you'll be doing it for You'll join the mobile platform team on a UK government app, working on the app and the services that support it. The team builds and maintains the common parts of the app, such as login. It also brings in key features built by other teams, and manages app releases. You're engaged through hedgehog lab, a digital product consultancy and certified B Corp, also Great Place to Work certified. For 20 years we've helped public and private sector organisations through digital transformation. What you'll be doing You'll build and improve the common parts of the Android app, such as login, in Kotlin with Jetpack Compose. You'll also work on how features built by other teams fit into the app. When your...

Software Engineer – Ruby (AI Training) About The Role What if your Ruby expertise could directly influence how AI writes and understands backend code for developers around the world? We're looking for experienced Ruby Software Engineers to work on real-world software systems that power data-driven and AI-supported workflows — reviewing, building, and evaluating production-grade code that helps train the next generation of AI models. This is a fully remote, flexible contract role. Work asynchronously on your own schedule, take on as many hours as suits you, and make a tangible impact on how AI reasons about software engineering. Organization: Alignerr Type: Hourly Contract / Task-Based Location: Remote Commitment: 10–40 hours/week What You'll Do Develop and maintain backend services and APIs using Ruby and Ruby-based frameworks Review and analyze existing codebases for correctness, performance, and maintainability...

Systems Programmer — AI Data Pipelines About The Role What if your mastery of Rust could directly shape the infrastructure powering the world's most advanced AI systems? We're looking for a senior Rust engineer to design and build the high-performance data pipelines, annotation tooling, and evaluation systems that leading AI labs depend on to train and improve their models. This is a fully remote contract role working on real production systems — not toy projects. You'll be embedded alongside world-class data, research, and engineering teams, solving hard systems problems that have a direct impact on the trajectory of AI development. Organization: Alignerr Type: Hourly Contract Location: Remote Commitment: 20–40 hours/week What You'll Do Design, build, and optimize high-performance systems in Rust supporting large-scale AI data pipelines and evaluation workflows Develop full-stack tooling and backend services for data...

Backend Developer — AI Data Services About The Role What if your C# expertise could directly shape the infrastructure powering the next generation of AI? We're looking for a Senior C# Full-Stack Engineer to build and optimize the data pipelines, annotation tooling, and evaluation systems that leading AI labs depend on to train and improve their models. This is a fully remote contract role with meaningful, high-impact work — the kind where your code doesn't just sit in a backlog, it actively influences how AI systems learn and behave at scale. Organization: Alignerr Type: Hourly Contract Location: Remote Commitment: 20–40 hours/week What You'll Do Design, build, and optimize high-performance C# systems supporting AI data pipelines and evaluation workflows Develop full-stack tooling and backend services for large-scale data annotation, validation, and quality control Improve reliability, performance, and safety across...

Job Description: Project Overview We are seeking a highly skilled and certified AWS Cloud Security & Frontend Engineer to conduct an intensive and comprehensive security assessment, infrastructure mapping, functional review and technical documentation of our platform. The target delivery window is 1–2 weeks. We are looking for an all-round Full-Stack Developer to work with us 5 days a week to also cover all aspects of our websites, including frontend and backend development, AWS infrastructure, deployment, maintenance, troubleshooting, security and SEO. The role requires someone who can take ownership of our web platforms and manage their ongoing development and performance. The business operates on Amazon Web Services (AWS) infrastructure, with Next.js cloud-based web applications, integrated Machine Learning APIs and a MySQL backend database. Scope of Work & Key Deliverables Application & Frontend Security Assessment: Evaluate Next.js...

Senior AWS DevSecOps & Next.js Consultant – Security & Infrastructure Audit Project Overview We are seeking a highly skilled and certified AWS Cloud Security & Frontend Engineer to conduct an intensive and comprehensive security assessment, infrastructure mapping, functional review and technical documentation of our platform. The business operates on Amazon Web Services (AWS) infrastructure, with Next.js cloud-based web applications , integrated Machine Learning APIs and a MySQL backend database . The target delivery window is 1–2 weeks . Scope of Work & Key Deliverables Application & Frontend Security Assessment: Evaluate Next.js codebases, Server-Side Rendering (SSR) security, API routes and frontend security controls against recognised industry standards, including OWASP Top 10 and CIS Benchmarks . AWS Infrastructure & Database Audit: Conduct a comprehensive security assessment of our AWS environment,...

Are you a coding expert fluent in Python eager to shape the future of AI? Large‑scale language models are evolving from clever chatbots into powerful engines of scientific discovery. With high‑quality training data, tomorrow's AI can democratize world‑class education, keep pace with cutting‑edge research, and streamline software development for engineers everywhere. That training data begins with you—we need your expertise to help power the next generation of AI. We're looking for Python coding specialists who live and breathe algorithms, data structures, software architecture, frontend and backend development, cloud infrastructure, and systems programming—and who can do so fluently using Python. You'll challenge advanced language models on topics like asynchronous programming, RESTful API integration, memory management, object-oriented design, secure coding practices, and debugging distributed systems—documenting every failure mode so we can harden model...

About the Role What if your precision with YAML configurations and structured data could directly influence how AI systems understand and operate in the real world? We're looking for detail-oriented Software Engineers to review, author, and evaluate YAML-based configurations and workflows — helping ensure the AI systems powering tomorrow's technology are built on a solid, reliable foundation. This is a fully remote, flexible contract role designed for engineers who love working close to the metal — configuration files, schemas, and system logic are your natural habitat. Organization : Alignerr (Powered by Labelbox) Type : Hourly Contract Location : Remote Commitment : 10–40 hours/week What You'll Do Author, review, and maintain YAML files used for configuration, data pipelines, and system definitions Ensure YAML structures are accurate, well-organized, and compliant with required schemas Identify formatting issues,...

Lead DevOps Engineer (Contract, Outside IR35) Contract:  Outside IR35 Start date:  December 2026 Length:  Three months initially, with a chance to extend Location:  Remote first, based within 50 miles of Edinburgh, Newcastle, Leeds, Manchester or London A lot of DevOps contracts drop you into someone else's setup and ask you to keep it running. On this one, you'll decide how it's built. What's in it for you You'll lead the DevOps work from day one, with the authority to make decisions and see them through. You'll join a team that already knows what good looks like, so you won't spend your first month untangling things. Who you'll be doing it for You'll be working for hedgehog lab, a digital product consultancy with 20 years of experience. We're around 100 people, B Corp and Great Place to Work certified, and backed by a growth capital investor. Your clients will be public and private sector organisations going through digital...

Are you a coding expert fluent in Python eager to shape the future of AI? Large‑scale language models are evolving from clever chatbots into powerful engines of scientific discovery. With high‑quality training data, tomorrow's AI can democratize world‑class education, keep pace with cutting‑edge research, and streamline software development for engineers everywhere. That training data begins with you—we need your expertise to help power the next generation of AI. We're looking for Python coding specialists who live and breathe algorithms, data structures, software architecture, frontend and backend development, cloud infrastructure, and systems programming—and who can do so fluently using Python. You'll challenge advanced language models on topics like asynchronous programming, RESTful API integration, memory management, object-oriented design, secure coding practices, and debugging distributed systems—documenting every failure mode so we can harden model...

About The Role What if the code you write could directly shape how the next generation of AI understands and generates software? We're looking for Software Engineers in London to build, evaluate, and improve AI-generated code — helping train AI systems to think like real developers. You'll write solutions, review AI outputs, and provide the expert-level feedback that makes AI coding assistants smarter, safer, and more reliable. This is hands-on engineering work at the frontier of AI development — not theoretical, not bureaucratic, and not boring. This is a fully remote, flexible contract role. If you can write clean code and explain your reasoning, we want to hear from you. Organization: Alignerr Type: Hourly Contract Location: Remote Commitment: 10–40 hours/week What You'll Do Write, debug, and optimize code across a range of languages, frameworks, and problem domains Review and evaluate AI-generated code for correctness,...

Are you a coding expert fluent in Python eager to shape the future of AI? Large‑scale language models are evolving from clever chatbots into powerful engines of scientific discovery. With high‑quality training data, tomorrow's AI can democratize world‑class education, keep pace with cutting‑edge research, and streamline software development for engineers everywhere. That training data begins with you—we need your expertise to help power the next generation of AI. We're looking for Python coding specialists who live and breathe algorithms, data structures, software architecture, frontend and backend development, cloud infrastructure, and systems programming—and who can do so fluently using Python. You'll challenge advanced language models on topics like asynchronous programming, RESTful API integration, memory management, object-oriented design, secure coding practices, and debugging distributed systems—documenting every failure mode so we can harden model...