Top Software Engineer Jobs in Belfast

The Junior Ubuntu Software Engineer will design, build, and ship software, focusing on quality and resilience, while engaging with the open source community.

Lead Mark43's AI-enabled engineering initiative by designing and orchestrating multi-agent systems that plan, write, review, test, and deploy software. Write prompts, scaffolding, and tool integrations (VCS, test runners, internal APIs), evaluate agent performance, prototype LLM-based workflows, collaborate cross-functionally, mentor teammates, and contribute to on-call rotations.

Designs, develops, and operationalizes large-scale backend, API, graph, AI, and machine learning solutions. Responsibilities include technical leadership, cloud-native architecture, roadmap development, testing, code reviews, mentoring, recruitment, stakeholder communication, and improving engineering processes. The role requires extensive Java and Spring experience, AWS cloud development, RESTful APIs, stream processing, low-latency applications, generative and agentic AI, and strong software delivery practices.

Build and productionize tooling that compiles complex Python packages such as NumPy, SciPy, and PyTorch from source. Develop conda recipes, build tools, automation, and release processes; partner with packaging and distribution teams; mentor engineers; and lead postmortems, capacity planning, and incident response. The role also shapes technical strategy, architecture, project scope, and delivery decisions for build and distribution infrastructure.

Design and build GitLab Duo CLI features in TypeScript, shape AI-assisted developer experiences, improve CLI reliability, observability, and performance, collaborate across Developer Clients, and provide technical leadership and mentorship.

Build and maintain production REST APIs using Java 21 and Spring Boot while developing AI-powered portal features with Python on GCP. Responsibilities include creating MCP and agent tooling, shipping LLM-backed products, managing Kubernetes and cloud services, modernizing legacy Java systems, conducting code reviews and testing, and advancing AI-assisted development practices across the engineering team.

Build and maintain the control planes, automation, and observability for a global fleet of machines. Develop production-quality Go services for provisioning, health checks, upgrades, and incident remediation. Architect high-throughput, low-latency networking, improve utilization and power-to-performance, and collaborate with product and platform teams on storage-aware scheduling and developer-facing features.

Design, build, and maintain backend API and database services for a cloud PBX platform. Drive architecture, performance optimization, debugging, CI/CD and test automation, and collaborate with QA. Mentor peers and raise engineering standards while safely evolving high-load, networked systems.

Leads quality engineering for consumer-facing web and mobile experiences. Designs scalable automation frameworks, develops functional, API, integration, regression, and end-to-end test suites, and integrates quality gates into CI/CD pipelines. Validates accessibility, performance, reliability, and cross-device behavior; investigates defects, analyzes quality metrics, and drives continuous improvement. Collaborates with product and engineering teams, mentors engineers, and applies AI-assisted testing practices.

Build and operate scalable, low-latency APIs, event-driven services, integrations, and web applications supporting membership and loyalty experiences. Integrate and extend Antavo with commerce, CRM, CDP, marketing, and data platforms. Apply distributed-systems, reliability, observability, and security practices; troubleshoot production issues; contribute to reusable engineering assets; and mentor junior engineers.

Design, build, optimize, and support scalable consumer-facing mobile applications across iOS and Android using React Native, TypeScript, and JavaScript. Develop native integrations, reusable components, secure architectures, API integrations, automated testing, CI/CD pipelines, and production monitoring. Collaborate cross-functionally, contribute to releases and Agile delivery, mentor engineers, conduct code reviews, and drive mobile engineering excellence, accessibility, performance, and reliability.

Build and maintain Clojure-based software to accelerate medical device regulatory approvals. Work cross-functionally to deliver high-quality safety assessments, ship features quickly, and support product growth. Remote-first, collaborative environment with occasional in-person weeks in London.

Responsible for designing and implementing authentication features in Go and TypeScript, enhancing Auth architecture, and collaborating with teams to improve user experience.

Join Uncountable's Implementations Engineering team to build software that integrates R&D lab instruments with their platform, working closely with customers and developing automated data pipelines.

Design, maintain, and scale backend services and APIs connecting Phantom Cash to blockchains. Build reliable event-driven systems with REST APIs, distributed-system patterns, retries, idempotency, and data consistency. Collaborate across teams, document decisions, mentor engineers, and improve engineering standards. The role also involves blockchain integrations, operational ownership, observability, and delivering dependable financial products in a remote crypto environment.

Freelance software developer responsible for designing, developing, testing, and maintaining high-performance applications. Collaborate with cross-functional teams to deliver innovative, client-focused solutions on a remote, on-demand platform.

Join ROOST's Coop project to design, implement, test, document, and release trust-and-safety features. Work across backend APIs, GraphQL, databases, and UI to improve reviewer workflows, detection integrations, and reporting. Lead code quality, security practices, community contribution reviews, and stakeholder coordination while engaging with users and the open source community.

Join the ROOST Osprey team to design, implement, test, and maintain a high-performance, real-time safety rules engine. Work includes building data/event pipelines, scaling and containerizing services, integrating with Kafka and gRPC, reviewing community contributions, maintaining code quality and security, and engaging with users and open source contributors to prioritize and deliver features.

Build a decentralized, serverless P2P search stack using Node.js. Implement and evaluate distributed indexing, DHTs, CRDTs, and networking (NAT traversal, encryption, multiplexing). Optimize protocols and high-concurrency networking code and work with the Holepunch stack components like hyperdht and hyperswarm.

As a Backend Software Engineer, you'll develop and maintain REST APIs using Django, manage cloud infrastructure, and oversee CI/CD pipelines to support consumer fintech applications.

As a Software Engineer, you will build and maintain financial platforms and applications that help homeowners track and manage their expenses, collaborate with the engineering team, and utilize AI for data insights.

As a Software Engineering Intern, you will contribute to building features for user-facing products, APIs, and scalable services for machine learning. Responsibilities include crafting code, designing data pipelines, implementing tools, and enhancing technical documentation.

Lead technical teams to design, build, test, and maintain modern, scalable, secure software. Provide technical ownership for product architecture, estimation, planning and requirements. Coach and develop junior staff, drive CI/CD practices, troubleshoot live applications, and liaise with customers as the teams technical leader.

Build and operate stateful streaming pipelines and Go services that process usage events into accurate, near-real-time billing data. Responsibilities include ingestion, validation, enrichment, pricing, storage integration, usage APIs, billing exports, failure recovery, idempotency, exactly-once processing, reconciliation, scalability, observability, and deployment ownership.

Design and build distributed backend services for the cloud monetization platform, focusing on correctness, consistency, scalable microservices, distributed transactions, and reliable asynchronous workflows. Influence system architecture, own service implementations, and collaborate across teams to support billing, reservations, payments, and revenue flows.