64 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:...

About nsave nsave is a fintech company headquartered in London. Founded by Amer Baroudi and Abdallah AbuHashem, our vision is to "Protect and grow the wealth of the financially excluded". We have built a global platform that provide trusted USD accounts, global payments, and investments for individuals from distressed economies, where inflation is high and banking systems are unstable. Our compliance-by-design approach and proprietary technology allow us to deliver these services securely and at scale. To date, nsave has raised $22M from leading investors including Sequoia Capital, TQ Ventures, Y Combinator, and SV Angel. Our team has grown 200% in the last year, and with so much more ahead, we're just getting started! Learn more at www.nsave.com . Location: Egypt (Cairo preferred) Engagement Type: Independent Contractor About the Role As our Backend Engineer , you will build and scale the infrastructure powering nsave's financial services. Working...

(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...

About nsave nsave is a fintech company headquartered in London. Founded by Amer Baroudi and Abdallah AbuHashem, our vision is to "Protect and grow the wealth of the financially excluded". We have built a global platform that provide trusted USD accounts, global payments, and investments for individuals from distressed economies, where inflation is high and banking systems are unstable. Our compliance-by-design approach and proprietary technology allow us to deliver these services securely and at scale. To date, nsave has raised $22M from leading investors including Sequoia Capital, TQ Ventures, Y Combinator, and SV Angel. Our team has grown 200% in the last year, and with so much more ahead, we're just getting started! Learn more at www.nsave.com . Location: Egypt (Cairo preferred) Engagement Type: Independent Contractor About the Role As our Backend Engineer , you will build and scale the infrastructure powering nsave's financial services....

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...

Role description Senior AI Infrastructure Engineer (Agent Runtime Platforms) London – Hybrid ASAP 6 month Contract Inside IR35/ Fixed Term Employment   UST is looking for a Senior AI Infrastructure Engineer with deep experience building and operating production-scale agentic AI systems. You'll work with leading agent runtime platforms such as Amazon AgentCore Runtime (or similar) to deploy, secure, and scale AI agents and multi-agent workflows across enterprise environments.   What You'll Do: Deploy and manage AI agents and multi-agent systems in production Configure agent runtimes, tool integrations, permissions, and access controls Design memory, state management, and context-handling architectures Implement AI guardrails, governance, monitoring, and observability Build Python-based APIs, platform services, and orchestration layers Develop scalable, cloud-native AI solutions on AWS Contribute reusable...

Posted 1 hour ago  Contract  Competitive     AI Engineer - 12 Month Day Rate Contract Job Introduction Handelsbanken combines a long-established relationship banking model with secure, resilient, and customer-focused technology. Our technology teams enable the Bank's decentralised way of working, delivering systems built for stability, trust, and long-term value. We are on a multi-year technology and digital transformation journey to enhance customer experience and improve how colleagues work together. By modernising platforms, simplifying processes, and better connecting data and systems, we help relationship teams focus on customers and less on complexity. Our decentralised culture extends to technology. Teams are trusted to take ownership, make informed decisions, and deliver sustainable, high-quality solutions. We value engineering excellence, pragmatic problem-solving, and strong collaboration across technology, business, and...

AI Engineer - 12 Month Day Rate Contract Job Introduction Handelsbanken combines a long-established relationship banking model with secure, resilient, and customer-focused technology. Our technology teams enable the Bank's decentralised way of working, delivering systems built for stability, trust, and long-term value. We are on a multi-year technology and digital transformation journey to enhance customer experience and improve how colleagues work together. By modernising platforms, simplifying processes, and better connecting data and systems, we help relationship teams focus on customers and less on complexity. Our decentralised culture extends to technology. Teams are trusted to take ownership, make informed decisions, and deliver sustainable, high-quality solutions. We value engineering excellence, pragmatic problem-solving, and strong collaboration across technology, business, and risk. We offer technologists the opportunity to build lasting careers, deepen their...

AI Engineer - 12 Month Day Rate Contract Job Introduction Handelsbanken combines a long-established relationship banking model with secure, resilient, and customer-focused technology. Our technology teams enable the Bank's decentralised way of working, delivering systems built for stability, trust, and long-term value. We are on a multi-year technology and digital transformation journey to enhance customer experience and improve how colleagues work together. By modernising platforms, simplifying processes, and better connecting data and systems, we help relationship teams focus on customers and less on complexity. Our decentralised culture extends to technology. Teams are trusted to take ownership, make informed decisions, and deliver sustainable, high-quality solutions. We value engineering excellence, pragmatic problem-solving, and strong collaboration across technology, business, and risk. We offer technologists the opportunity to build lasting careers,...

Senior Generative AI Scientist – Agentic AI & Multi-Agent Systems London (Hybrid, 3 days onsite) Contract (Inside IR35) or Fixed-Term Employment   UST is seeking a hands-on Senior Generative AI Scientist to design, build, and deploy production-grade AI solutions that solve real business problems. You will work with engineering teams, AI specialists, and business stakeholders to deliver scalable agentic AI systems, multi-agent workflows, and enterprise GenAI applications.   The Role: Design and develop multi-agent AI systems and orchestration workflows Build production-ready LLM applications and AI-powered automation solutions Develop and optimise RAG pipelines, retrieval architectures, and vector search solutions Build Python-based APIs, microservices, and orchestration services Design asynchronous, event-driven workflows and integrations Implement AI guardrails, evaluation frameworks, observability, and monitoring...

Role description Senior Generative AI Scientist – Agentic AI & Multi-Agent Systems London (Hybrid, 3 days onsite) Contract (Inside IR35) or Fixed-Term Employment   UST is seeking a hands-on Senior Generative AI Scientist to design, build, and deploy production-grade AI solutions that solve real business problems. You will work with engineering teams, AI specialists, and business stakeholders to deliver scalable agentic AI systems, multi-agent workflows, and enterprise GenAI applications.   The Role: Design and develop multi-agent AI systems and orchestration workflows Build production-ready LLM applications and AI-powered automation solutions Develop and optimise RAG pipelines, retrieval architectures, and vector search solutions Build Python-based APIs, microservices, and orchestration services Design asynchronous, event-driven workflows and integrations Implement AI guardrails, evaluation frameworks,...

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...

Must have skills: Demonstrable experience with Solidity. Strong understanding of blockchain security practices and potential vulnerabilities. Proficiency in Hardhat and Foundry. Experience with Solidity security testing tools like Slither, Mythril, Echidna Practical experience with scripting languages like Javascript or Typescript. Ability to craft unit, integration, fork, and invariant tests, ensuring code longevity. Demonstrable aptitude for best development practices, data structures, algorithms, and methodologies. Bachelor's degree in Computer Science, Engineering, or a related STEM discipline. Excellent debugging and troubleshooting skills. Strong written and verbal communication skills. Self-motivated with the ability to work in a fast-paced, evolving environment. Proficient communication skills in English. Development background in sectors such as banking, finance, or trading, paired with a comprehensive grasp of financial...

3-4 days per week, hybrid work policy in central London office We're looking for a freelance product engineer to join us between June and October 2026, working primarily on wonderbly.com with a focus on driving growth into Q4. This is a hands-on role. The work involves close collaboration with the VP product and other teams to solve deep customer experience challenges around our Kids and Keepsake landing pages and journeys, in order to unlock growth in these key areas for the business. You'll be working within a small, focused team — and at least some of the time, with a fair amount of autonomy. We're not looking for someone to execute a perfect brief. We're looking for someone with the judgment to help us figure out the right thing to build, and then build it well. A few things that are important to us The work you're doing feeds directly into beautifully made, deeply personal books that people treasure. People’s perception of quality has to be...

What’s Yonder? “It's as if Time Out, Amex and Monzo had a baby” - Will T, Yonder Member Yonder combines credit and debit in one membership that’s fair, flexible and actually enjoyable. No jargon. No dusty points system. Just rewards that actually feel rewarding, from bao to beer to a boarding pass. The engineering team sits at the heart of the company; we work in squads alongside product and design, and closely with risk, compliance, operations and partnerships. Sounds cool. What’s my part in this? We’re looking for an experienced Senior Product Engineer on a 3-month contract to add delivery capacity to our engineering team. The work is primarily Scala backend, but we don’t believe in rigid boundaries; everyone is encouraged to contribute wherever the problem takes them, whether that’s infrastructure, the mobile app (React Native) or the webapp (Next.js). You’ll be working alongside a small engineering...

Location: London (Hybrid – 3 days onsite, mandatory) Employment Type : Permanent | Fixed-Term Contract | Contract (Inside IR35) Start Date : Immediate/ Short Notice period About the Role We are seeking a Senior AWS Application & Platform Engineer to help design and build cloud-native applications, developer platforms and AI-enabled engineering capabilities from the ground up.   This is a highly hands-on engineering role combining AWS application development, serverless and event-driven architecture, Python, Generative AI, developer tooling and automation.   You will build APIs, reusable application patterns, developer accelerators and AI-enabled services that help engineering teams deliver software more efficiently, securely and consistently.   Key Responsibilities Design and build cloud-native applications, APIs and platform services on AWS. Develop serverless and event-driven solutions using AWS Lambda, API...

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...

Job Title: AI Roku Developer Location: London Company: BritBox International Reporting to: SVP of Technology and Content Delivery Contract Type: Day rate Contractor, 3-month About Us BBC Studios’ Direct-to-Consumer (DTC) business brings premium content directly to North American audiences through two distinctive streaming brands: BritBox and BBC Select. BritBox , the ultimate streaming destination for British TV. We offer an unparalleled collection of thoughtfully curated entertainment—cleverly crafted and full of the charm, wit, and heart that define British storytelling. Born from the BBC, our mission is to bring authentic British stories to our audiences. Launched in 2017, we are a small but mighty streamer that punches above our weight—available on every major platform and even featured among the bright lights of Times Square—and we’re just getting started. BBC Select is a documentary streaming service that has been...

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...