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.

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.

You will work with Java, Selenium, RestAssured, Gherkin, and Jira/Xray to design and maintain automated test frameworks. This cross-functional Agile squad develops complex healthcare software systems that support Genomics England’s genomic medicine and research initiatives for the NHS.

Design, build, and deploy quantitative models using Python, R, and libraries (numpy, pandas, scikit, pytorch, tidyverse, caret, ggplot) plus NLP tools, SQL, AWS, Sagemaker, DataBricks, Snowflake, MLFlow, and Weights & Biases. The team creates systematic country risk analytics and ML/NLP pipelines for BMI’s market insights, supporting clients in risk assessment.

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.

As Principal SDET, you will lead quality engineering using C#, Playwright, and Selenium for test automation across UI, API, and integration layers. You will drive the quality strategy for a financial services organisation undergoing a major business and technology transformation. This is a senior technical leadership role, not managing a specific team size.

Work with Python, BeautifulSoup, Selenium, and Apify to scrape dynamic web content, extract data from complex structures, and deliver structured datasets. You will join the Tendem project, driving specialized data scraping workflows for real-world applications. LLM and AI frameworks are also used to enhance automation.

Fitch Solutions★3.0 (2)· London

As a Data Scientist at BMI (a Fitch Solutions business), you will design, build, and deploy quantitative models using Python and R (e.g., numpy, pandas, scikit, pytorch) to power advanced analytics. You will develop and maintain ML/NLP and data pipelines, working with Economists and Analysts to build risk models and generate insights from structured and unstructured data.

American Express★4.1 (9.7k)· London

You will work with Kotlin/JVM, Java, React, Postgres, MongoDB, Redis, Docker, Kubernetes, and GitHub Actions. The Financial Insights and Tools group builds financial analysis software for American Express customers, powered by APIs and underlying platforms for web and mobile applications.

You will work with Java, JavaScript, Python, or C#; open-source frameworks like Cypress, Karate, PlayWright, or Selenium; CI/CD pipelines in Azure DevOps; and JMeter for performance testing. As part of an agile team, you’ll help clients achieve business transformation goals through automated and manual testing.

Work with Kotlin/JVM, Java, React, APIs, Postgres, MongoDB, Redis, Docker, Kubernetes, GCP GKE, AWS ECS/EKS, Ktor, Spring, and GitHub Actions. The Financial Insights and Tools group builds customer-facing web and mobile features that aggregate and analyze financial data to enhance personal finance management.

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.

Use Selenium with C# to build and maintain automation frameworks, create regression suites, and perform functional/integration testing. As the first UK-based QA for a financial services firm's growing European technology team, you'll collaborate with an Agile squad and a US QA team.

American Express★4.1 (9.7k)· London

Work with Kotlin/JVM, Java, React, Postgres, MongoDB, Redis, Docker, Kubernetes (GCP GKE, AWS ECS/EKS), GitHub Actions, Ktor, and Spring. The Financial Insights and Tools group within Digital Banking builds financial analysis and planning applications for American Express customers on web and mobile, powered by APIs.

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.