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.

Zoopla★3.9 (18)· London

A 12-month maternity cover role on a dual-stack C#, .NET, and TypeScript backend with React microfrontends, using AWS managed services (ECS/Fargate, Lambda, SQS, DynamoDB, DocumentDB) and Terraform/SST. You'll build B2B SaaS software for estate agents and home builders at Alto Software Group. Take end-to-end ownership of features from design to production, working with the product team and AI coding agents.

DeepL★3.8 (4)· London

You'll work with C# / .NET, RESTful APIs, distributed architectures, and optionally React/TypeScript, plus MCP, CLIs, OAuth, and AI coding tools. You join the API Enterprise team, which builds enterprise adoption features (usage insights, cost controls, RBAC, compliance, data residency) for DeepL's Language AI API platform.

Checkout.com★3.8 (15)· London

Senior Engineering Manager leading the Disputes team, which builds tools, services, and machine learning models to help merchants manage and win chargeback disputes at scale. The team owns a full stack centered on .NET / C#, React and TypeScript front ends, Python-based ML, and event-driven microservice architectures.

You will work with C# / .NET, modern front-end frameworks (Blazor, React, Angular, or Vue), and cloud platforms (AWS, Azure, or GCP) on the Web team. This team builds web frameworks powering TradingHub’s MAST and CaaS trade surveillance products for financial institutions.

Capital on Tap★3.9 (55)· London

First and foremost a software engineering role, you will work with C#, .NET, agentic systems and orchestration layers, and AI enablement tooling. You will build "AI on Tap", the company's internal hub for AI agents, and integrate agentic testing/verification across the pipeline to accelerate delivery for this financial platform.

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.

You'll develop full-stack software products using TypeScript, React, Python, Node.js, Java/Spring, C#/.NET, SQL, NoSQL, vector databases, LLM frameworks, and cloud platforms (Azure, AWS, GCP) with Docker and CI/CD. QuantumBlack, AI by McKinsey is a multidisciplinary group creating industry-shaping digital products and tools for clients across industries. You'll work hands-on with global technologists, designers, and strategists to build cutting-edge solutions while mentoring client teams on engineering practices and Agile values.

You'll work with frontend (TypeScript, React, Angular, Vue, Next.js, Tailwind), backend (Python, Node.js, Java/Spring, C#/.NET), databases (SQL, NoSQL, vector databases), LLM frameworks, and cloud platforms (Azure, AWS, GCP) including Docker and CI/CD. QuantumBlack, an AI division of McKinsey, builds industry-shaping products and tools across diverse industries by pairing software engineers, AI engineers, and data scientists with client leadership. As a Senior Software Engineer, you'll lead architecture design, mentor teams in engineering excellence and Agile practices, and drive technology decisions on scalable solutions.

Build and maintain the company’s platforms using JavaScript, Node.js, Next.js, Express.js, React/React Native, .Net 4.8/9/10, C#, HTML/CSS, and API Restful Services. You will develop both web and mobile applications, collaborating with the team while working independently.

DeepL★3.8 (4)· London

You will work with C#/.NET Core, Python, React, and Kubernetes, plus AI-assisted tools like Copilot and Claude. You’ll ship end‑to‑end user‑facing features for DeepL’s Language AI platform, which provides human‑like translation, improved writing, and real‑time voice translation to millions of users and businesses globally.

DeepL★3.8 (4)· London

You will work with React, C#/.NET, and AI-powered tools like GitHub Copilot and Claude, building full-stack Enterprise features. The team, part of DeepL’s Business Acceleration Track, architects the company’s revenue and billing systems, including Identity & Access Management and subscription architectures for global enterprises.

DeepL★3.8 (4)· London

Work with C#/.NET Core, Python, Kubernetes, and React on DeepL’s Language AI platform—building translation, writing, and real-time voice solutions used by over 300 million users globally. You will own revenue-critical systems end-to-end, from architecture to production.

Checkout.com★3.8 (15)· London

You'll work with REST/JSON APIs, Postman, JavaScript, React, Angular, Java, .NET, Python, Node, and payment technologies like 3DS, tokenisation, and Apple/Google Pay. As a Sales Engineer, you'll support clients integrating Checkout.com's online payments platform, which powers transactions for companies like eBay, Uber, and Spotify.

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 .NET, Java, Python, TypeScript and AI coding tools such as GitHub Copilot, Claude Code or Codex. You will lead a small engineering team driving an AI-first transformation at a growing technology business, shaping engineering strategy and building modern, AI-ready foundations.

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.

You will work with C#, ASP.NET Core, React/Angular/Blazor, REST APIs, Git, Azure/AWS, and CI/CD tools. The role is with 83zero, though the listing does not specify a particular team or product project.

You will work with C#, the latest .NET platform, and SQL Server, Oracle, or equivalent relational databases. The role is being recruited by Spectrum IT Recruitment, a tech recruitment firm.

You will work with C#, .NET, SQL, Git, Azure DevOps, Microsoft Azure, and APIs to develop, maintain, and enhance business-critical applications for Hays Technology.

You will design, build, and ship C# applications using .NET and Azure, potentially including Azure DevOps, Azure Functions, and AKS/Kubernetes. The role is at a boutique technology consultancy where you work across diverse client projects in various sectors.

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.

You'll work with .NET and C# on custom analytics platforms that drive private equity investment decisions. The role involves both building new platforms and improving existing features, with real ownership over your approach.