Top Software Engineer Jobs in Madrid

Build end-to-end full-stack AI features on a Ruby on Rails backend and React frontend, including LLM inference infrastructure, RAG, AI agents, and evaluation/observability. Design and run experiments (A/B tests), optimize systems for production performance and reliability, and iterate rapidly with product and design partners.

Build and evolve Circle Discover marketplace features: high-converting purchasing flows, algorithmic recommendations, content feeds, and listings. Work across a Ruby on Rails backend and React/Next.js front-ends, optimize performance and SSR/SSG, collaborate with designers and leaders, and improve codebase quality while shipping at pace in a distributed remote team.

The Software Engineer will join a product squad to develop and maintain functionalities on the 360Learning platform, focusing on JavaScript technologies and clean architecture.

Build scalable backend systems and data pipelines to power consumer credit reporting. Partner with Product, Compliance, Servicing, and Credit teams to design, deliver, monitor, and operate accurate reporting systems, including on-call responsibilities. Develop robust, well-tested code in Python or Kotlin using distributed systems patterns and technologies like AWS, MySQL, and Spark.

Work on Servicing International building purchase protection (disputes/refunds) and agent tooling. Contribute to web apps and backend APIs, collaborate with global teams, participate in on-call rotation, ship reliable scalable solutions, and engage in code reviews and growth activities.

Design, build, and deploy production-grade agentic AI systems: multi-agent orchestration, RAG pipelines, provider integration, LLMOps, observability, and reusable patterns. Embed with client teams, lead design sessions, tune embeddings/vector search, manage cost/latency tradeoffs, and define metrics for accuracy, safety, latency, and cost.

Design, build, and maintain backend collections systems to manage delinquent loans. Collaborate with product, risk, and engineering teams, deliver features in phases, support operations and on-call rotation, instrument monitoring, and participate in hiring and team growth.

Lead design and delivery of real-time fraud decisioning services and APIs, extend decisioning platform to international markets, integrate regional risk vendors and ML/AI signals, own platform tooling and availability, mentor engineers, collaborate cross-functionally, and participate in on-call rotation.

Build and maintain backend collections systems to manage delinquent loans, implement recovery strategies, ensure high availability and reliability, collaborate with product and risk teams, participate in on-call rotation, write well-tested extensible code, and contribute to team growth.

You will lead engineering efforts for backend system development, collaborate with global teams, ensure operational availability, and develop talent on your team.

Lead design and development of low-level Linux instrumentation and eBPF-based runtime security features for detection, monitoring, and workload protection. Drive architecture, implement performance-sensitive systems, establish testing methodologies, deliver end-to-end features, and provide technical leadership and cross-team collaboration across Datadog's security products.

Lead and deliver backend features for Repayment Scheduling: design and implement highly available distributed systems, collaborate with product/design/analytics, own operational reliability and on-call duties, mentor engineers, set quality standards, and drive technical decisions and delivery.

Own and deliver backend identity systems for international markets, shaping technical direction, designing distributed, highly available services, and collaborating with product, design, and analytics. Improve reliability, performance, and operational health; participate in on-call rotation; set code and design standards; mentor and grow engineers; reduce toil and create runbooks/playbooks. Drive cross-team collaboration to meet regulatory and market-specific identity/KYC requirements.

Build and maintain hardened Ubuntu-based container images and the automated CI/CD pipelines to build, test, scan, sign, publish, and retire them. Integrate upstream open-source projects, ensure security and cloud-native compatibility, collaborate with cross-functional teams, document and share knowledge, mentor colleagues, and contribute to hiring. Work in a distributed agile environment with occasional travel.

Build and scale a blockchain data platform handling petabytes of on-chain data. Design and implement distributed systems, data ingestion/decoding pipelines, and performant SQL processing. Write production code (Kotlin, Go, Java, Rust), improve developer experience, automate operations (including AI-driven automation), and own platform components.

Build and operate Grafana's bare-metal platform: provision storage, networking, and Kubernetes clusters; manage cluster networking, scheduling, and autoscaling; maintain Crossplane compositions and Terraform modules; collaborate with product teams; participate in on-call rotation and datacenter operations.

Lead and deliver Repayment UX features for Affirm's mobile products using React Native. Own quarterly goals, guide engineers through ambiguous problems, collaborate with product/design/analytics, ensure operational reliability (metrics and on-call), improve engineering standards, and mentor teammates to drive high-quality, scalable mobile experiences.

Develop and optimize algorithms for battery and renewable energy projects, analyze market data trends, and ensure algorithm performance.

Own and build a production-grade iOS client using Swift and SwiftUI. Integrate AI features via backend APIs, design AI UX flows (streaming, retries, fallbacks), optimize performance and battery, capture user signals for evaluation, collaborate with backend/ML engineers, and maintain App Store quality, stability, and reliability.

Own and build the Android client for an AI-first app: implement AI features (chat, vision, voice), optimize performance and memory, design UX for streaming and partial results, integrate backend APIs, instrument analytics/logging, and collaborate with backend and ML teams to ensure stability, security, and scalability in production.

Develop and maintain high-performance microservices, engage in the full software development lifecycle, and collaborate within autonomous teams. Understand service architecture and optimize solutions for scalability and resilience.

As a Backend Software Engineer, you'll design scalable backend systems, optimize database performance, and collaborate with front-end and DevOps teams.

Contribute to Juju's development, collaborate with teams on distributed systems, debug issues, and enhance cloud automation features.

Build ML prototypes and data pipelines, collaborate with researchers and product engineering to integrate models into Fusion, containerize and deploy applications, implement best practices, and document architectures to accelerate research-to-production workflows.

Develop and maintain complex React.js web applications; collaborate with designers and backend teams to build responsive, accessible UIs; write clean, scalable code; optimize performance; debug and support testing and deployment; mentor junior developers and follow Agile practices.