Citi★3.9 (21k)· London

Work with Solidity, Web3J/Web3JS/Ethers.js/Viem, Java/Spring, Node.js, and blockchains such as Ethereum, Hyperledger Besu, Canton, and Solana, using Hardhat/Foundry/Truffle for testing. Contribute to Citi's Integrated Digital Assets Platform (CIDAP) building Web3 components for tokenization, smart contracts, and on-chain settlement.

Backend engineers use Python, Django, Django-REST-framework, GraphQL (Graphene), Celery, Postgres, and AWS (Packer, Consul, Terraform). They build and maintain the AI-driven energy management platform that powers utilities and optimises renewable generation. The global engineering team is around 1,400 people.

Python micro-services with RabbitMQ and OpenShift/Kubernetes, using SQL Server and Parquet. The London Commodities Risk Technology team builds a front-office distributed platform for trading and risk calculations on assets like oil, gas, power, and exotics, collaborating with traders and quants.

Work with C# on .Net Framework 4.5.2+ and .Net 5+, using NUnit, xUnit, REST, Kafka/RabbitMQ, Git, and Linux. You will build Citi’s next-generation Equities technology platform for execution, clearing, and margin processes.

Koinly★3.0 (1)· London

Work with React 19, TypeScript, TanStack (Router, Query, Table), Radix UI, Mantine, Tailwind CSS v4, Vite, Vitest, Storybook, Highcharts, Sentry, Bun, and RabbitMQ on a data platform that reconciles crypto transactions and tax obligations for Koinly’s web application, with a React Native mobile app joining scope later.

Koinly★3.0 (1)· London

You will work with TypeScript on Bun, RabbitMQ, Redis, PostgreSQL, Vitest, Sentry, and Rust. The team owns the distributed data-processing backend that ingests, normalizes, and reconciles on-chain and exchange data for Koinly’s crypto tax calculation product.

Nuffield Health★3.2 (939)· London

You will work with Java 21, Spring Boot, Maven, RabbitMQ, Apache Camel, Git, GitHub Actions, Docker, Azure DevOps, Terraform, Ansible, and SQL databases. The Integration Squad designs, develops, and supports microservices and APIs for Nuffield Health's digital healthcare platforms, enabling secure connectivity across internal and third-party systems.

A full-stack or backend specialist will use C# and .NET Framework, SQL Server (T-SQL), RESTful APIs, Azure DevOps, and messaging queues (RabbitMQ, Kafka) to build secure integration pipelines and backend services. They will execute a critical integration programme for an international Wealth Management firm to connect core internal and third-party systems.

As a Backend Software Engineer, you'll use Go or Node.js to build and scale the company's core real-time messaging platform, working on low-latency Pub/Sub services and state synchronization in an AI-first engineering environment.

Python (3.10+) and Go development, with JavaScript/TypeScript for frontend; using RabbitMQ, Kafka, PostgreSQL, Redis, OpenTelemetry, and Prometheus. You will build and maintain low-latency real-time data feeds and web scraping pipelines to expand access to liquidity providers for sports prediction models.

G-Research★3.6 (18)· London

You will build automation frameworks and tooling using Python, Ansible, Terraform, and Jinja2, integrating them into CI/CD pipelines. This hands-on role sits at the intersection of networking and software engineering, developing APIs and self-service tools to power large-scale compute and research environments at a quantitative finance firm.

Design and build production-grade ML systems using MCP servers, recommendation systems, RAG pipelines, LLMs, and foundation models with Python, TensorFlow, PyTorch, FastAPI, and LangChain. You will own the end-to-end AI lifecycle for a sales data platform, deploying models into batch/real-time environments to drive forecasting, segmentation, and early warning systems. This role focuses on embedding context-aware intelligence into decision-making tools for business stakeholders.

DNEG★3.1 (36)· London

Design, build, and maintain high-performance RESTful APIs, microservices, and event-driven architectures using Python, PostgreSQL, and Redis. You will integrate generative AI models (ATMAN, VAANI) into production backends for a company operating at the intersection of enterprise Media Asset Management and generative media.

You will work with JavaScript (Angular), TypeScript, Python, FastAPI, Tailwind CSS, Docker, Kubernetes, and AWS. As part of a 13-strong Full Stack team, you'll build features for Urban Jungle’s insurance platform, collaborating with Product, Commercial, and Data.

Backend services using Python, Node.js, Java, and Go on AWS/GCP/Azure with Docker, Kubernetes, Kafka, RabbitMQ, SQL/NoSQL, and CI/CD. You will design, build, and support distributed systems for production-scale traffic, owning architecture and mentoring engineers.

Backend engineer using Java (preferred) or similar languages, Kafka or RabbitMQ, and SQL to build fraud detection and prevention systems for Wise's Receive Risk team. You'll support acquiring products like QuickPay and payment links, balancing seamless user experiences with strong fraud barriers across large-scale payment infrastructure.

Work with Python, Node.js, Java, Go, SQL, message queues, caching layers, Docker, Kubernetes, AWS/GCP/Azure, CI/CD, and optionally Kafka, RabbitMQ, Terraform, or Pulumi. You will design and build production-scale backend services, own full system lifecycles, and shape engineering standards.

You will architect and scale backend services using Python, FastAPI, and PostgreSQL, and work with message brokers like Azure Service Bus, RabbitMQ, or Kafka, plus Celery, Docker, and Kubernetes. The company builds an AI workspace processing sensitive financial data for large banks and regulated institutions under SOC 2, GDPR, and FCA compliance. You will report directly to the founders on a senior, staff-track IC team.

Backend Engineer role working with TypeScript, Node.js, Kafka, RabbitMQ, or SQS for event-driven and microservices architectures. You will build scalable backend services, APIs, and distributed systems for a FinTech platform that modernizes complex financial processes for institutional clients. The cross-functional team uses AI-assisted development tools.

Work across the stack with React, TypeScript, and Node.js or Golang on privacy-focused systems and architecture that keep users' location data inaccessible. As part of Wheely's small core-engineering team, you'll collaborate with Product Managers, Designers, and Software Engineers to shape solutions from concept through production.

Java, Spring Boot, React/Angular/Vue.js, PostgreSQL/MySQL, REST APIs, AWS/Azure/GCP, Docker/Kubernetes, Git, Maven/Gradle, and CI/CD. You will design, code, test, and maintain scalable Java applications for mission-critical systems as part of an agile squad.

You will build and scale White Circle's ecosystem partnerships across AI, cloud, infrastructure, and consulting. The company provides an AI safety platform that uses natural-language policies to test and enforce AI model behavior, and fine-tunes its own LLMs. You will work with the Head of Revenue to source, negotiate, and close partnerships driving revenue and distribution.

You'll set technical direction for a squad modernising a billing pipeline using TypeScript, Node.js, NestJS, PHP 8.x, Symfony, RabbitMQ, Kafka, SQS, PostgreSQL, GitLab CI/CD, and Grafana. The Interstellar Squad owns the mission-critical, event-driven billing run for Wireless Logic’s IoT connectivity platform.

Head of Quality Engineering to own quality across the organisation, working with PHP, Kotlin, GO, Python, Typescript, React, React Native, GraphQL, Relay, PHPUnit, Behat, JUnit, Kotest, Jest, Maestro, K6, Datadog, Sentry, Incident.io, Grafana, AWS, Docker, Kubernetes, RabbitMQ, Argo, Github, and Github Actions. The role will lead the use of AI (LLMs) for testing and will manage a team of approximately two Quality Engineers while being hands-on with code and CI pipelines. Lendable builds technology for consumer credit and savings products.

You'll ship code across Jay (Python, FastAPI, pydantic-ai) and a Laravel 11 core, with a frontend of Next.js, Nuxt and Vue, on AWS, using Claude Code and an in-house AI engineer. The team is building an AI agent that handles home setup and evolves into a Home OS for post-move tasks. You'll be one of a small, senior, AI-native engineering team.