16 senior backend engineer jobs found in London

OVERVIEW Senior Agentic AI Engineer / AI Architect - multi-agent AI systems London (4 Days Onsite) 6 month Contract (Inside IR35)   UST is seeking a Senior Agentic AI Engineer / Architect to design, build, and deploy enterprise-scale AI solutions powered by LLMs, Agentic AI, and Multi-Agent Systems. This is a hands-on role for someone who has moved beyond PoCs and has successfully delivered production-grade AI applications at scale. You'll work closely with architects, engineers, and business stakeholders to solve complex challenges using the latest AI technologies.   What You'll Do Design and develop multi-agent AI systems using modern orchestration frameworks. Build intelligent workflows leveraging agent planning, reasoning, memory, tool usage, and task delegation. Deliver production-ready solutions using LLMs, RAG, and AI-powered automation. Develop secure, scalable Python services, APIs, and orchestration layers....

Role description Senior Agentic AI Engineer / AI Architect - multi-agent AI systems London (4 Days Onsite) 6 month Contract (Inside IR35)     UST is seeking a Senior Agentic AI Engineer / Architect to design, build, and deploy enterprise-scale AI solutions powered by LLMs, Agentic AI, and Multi-Agent Systems. This is a hands-on role for someone who has moved beyond PoCs and has successfully delivered production-grade AI applications at scale. You'll work closely with architects, engineers, and business stakeholders to solve complex challenges using the latest AI technologies.     What You'll Do Design and develop multi-agent AI systems using modern orchestration frameworks. Build intelligent workflows leveraging agent planning, reasoning, memory, tool usage, and task delegation. Deliver production-ready solutions using LLMs, RAG, and AI-powered automation. Develop secure, scalable Python services, APIs, and...

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...

Senior Product Engineer (Freelance) Full job description 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...

Joining a new project Ideally have worked on Financial Services Projects before (Payments would be great) Fullstack Experience Tech Stack - Kotlin Backend, JS/TS React Frontend Start date ASAP Duration 6 months (Likely to extend) 2/3 days / week in person working (London) Immediate Interviews   The best bit about Red Badger is, of course, the team. We are really proud of our people; we support and learn a lot from each other; we work really hard but have fun doing it. We are a diverse group made up of 22 different nationalities, speaking 17 different languages.   Our 3 founders, Dave, Cain and Stu, who have considerable tech and consultancy experience and still own 100% of the company. We've been consistently profitable and have grown responsibly from the beginning.   We are based at Old Street in the heart of "tech city" and get thoroughly stuck in with the brilliant community around us. We run...

Location: London 1-2 days a week. Department: Engineering Employment Type: Contract Contract Length: 6 months (with potential for extension) About YLD: Our goal is to help our clients keep moving forward. We work with them to build the skills and capabilities they need to stay ahead of the competition, and we know our success only happens when they succeed. We’re a team of curious, talented people, and we’re committed to making YLD a place where great people want to work, grow, and stay. We’re a remote-first consultancy specialising in software engineering, product design, and data. Our teams are based across London, Lisbon, and Porto, and we create digital solutions that continue to deliver value long after our work is done. About the role: As a Senior Software Engineer at YLD, you’ll be part of a client team building innovative products. We’re looking for someone curious, passionate, driven, and...

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...

Senior Product Engineer (Freelance) Full job description 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...

We are looking for a Senior Fullstack Mobile Engineer with a strong emphasis on backend architecture to join the team developing a greenfield platform. You will own the end-to-end technical delivery of features, with the majority of your time focused on designing and building a robust, secure, and scalable backend using NestJS, Node.js and TypeScript . On the mobile side, you will contribute to feature integration and deployment within a React Native and Expo environment, ensuring seamless delivery across the full technology stack. The platform operates within a large enterprise technology ecosystem, so this role requires a senior engineer who is comfortable driving technical discussions, making architectural decisions, aligning infrastructure, and collaborating with neighbouring teams working across different technology stacks, including Kotlin and Spring Boot .   This role requires onsite time in Pimlico and sits inside IR35.   Backend...

Location: London 1-2 days a week. Department: Engineering Employment Type: Contract Contract Length: 6 months (with potential for extension) About YLD: Our goal is to help our clients keep moving forward. We work with them to build the skills and capabilities they need to stay ahead of the competition, and we know our success only happens when they succeed. We’re a team of curious, talented people, and we’re committed to making YLD a place where great people want to work, grow, and stay. We’re a remote-first consultancy specialising in software engineering, product design, and data. Our teams are based across London, Lisbon, and Porto, and we create digital solutions that continue to deliver value long after our work is done. About the role: As a Senior Software Engineer at YLD, you’ll be part of a client team building innovative products. We’re looking for someone curious, passionate, driven, and...

Joining a new project Ideally have worked on Financial Services Projects before (Payments would be great) Fullstack Experience Tech Stack - Kotlin Backend, JS/TS React Frontend Start date ASAP Duration 6 months (Likely to extend) 2/3 days / week in person working (London) Immediate Interviews   The best bit about Red Badger is, of course, the team. We are really proud of our people; we support and learn a lot from each other; we work really hard but have fun doing it. We are a diverse group made up of 22 different nationalities, speaking 17 different languages.   Our 3 founders, Dave, Cain and Stu, who have considerable tech and consultancy experience and still own 100% of the company. We've been consistently profitable and have grown responsibly from the beginning.   We are based at Old Street in the heart of "tech city" and get thoroughly stuck in with the brilliant community around...

Who Are We? Xcelirate develops technologically-advanced platforms which are accessed by thousands of users every minute! We are proud to offer a workplace where the sharpest developers come together to strategically plan and swiftly execute practices which see us maintain our existing market dominance and attain global expansion. We owe our success to our customers who have seen us grow across a decade, and our talented team who have made that growth possible!   What are we looking for? You're a Principal-Level Engineer first. The tech lead title is almost incidental. It just means you're the person the team orbits around, because that's what happens naturally when you're the one who understands the system most deeply and keeps the clearest head under pressure. The 10% that's people management fits inside your engineering work, not alongside it. You hire, you steer, you unblock, but you do it the way a strong engineer does everything: with good...

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...

We are looking for a Senior Fullstack Mobile Engineer with a strong emphasis on backend architecture to join the team developing a greenfield platform. You will own the end-to-end technical delivery of features, with the majority of your time focused on designing and building a robust, secure, and scalable backend using NestJS, Node.js and TypeScript . On the mobile side, you will contribute to feature integration and deployment within a React Native and Expo environment, ensuring seamless delivery across the full technology stack. The platform operates within a large enterprise technology ecosystem, so this role requires a senior engineer who is comfortable driving technical discussions, making architectural decisions, aligning infrastructure, and collaborating with neighbouring teams working across different technology stacks, including Kotlin and Spring Boot .   This role requires onsite time in Pimlico and sits inside IR35.   Backend...

Lead Java Developer/Solution Architect (6-month contract) Job description   gravity9 is recruiting Java engineers and architects for a portfolio of engagements across UK central government. These are large-scale, data-intensive modernisation programmes: replacing legacy systems that carry statutory weight, decomposing monoliths that serve millions of users, and building secure data platforms where access control and auditability are first-class architectural concerns rather than late additions. We are hiring across two overlapping profiles — Senior Java Developer and Application / Migration Architect — and expect most people to move between programmes as engagements start and complete. Several of these are hands-on architect roles: you will own design decisions and also write production code   The kind of work The following are representative of current and upcoming engagements. Individual roles will draw on some of this, not all of it...

Job Information Date Opened 25/08/2026 Job Type Contract Industry IT Services Work Experience 5+ years Salary £400 - £425 Outside IR35 About Scrumconnect Consulting Scrumconnect Consulting is a multi-award-winning digital consultancy, recognised for delivering impactful technology solutions across UK government departments. Our work has positively influenced the lives of over 40 million UK citizens. With a strong commitment to user-centred design and agile delivery, we continue to build innovative digital services that truly make a difference. Role Purpose We are looking for an experienced  Backend Developer  to design, build, and maintain scalable, secure server-side services and APIs, while contributing to the adoption of  Agentic AI  capabilities within our engineering platform. The role sits at  SFIA Level 4 : the individual works under general direction, uses discretion in resolving...