Software Engineer - Member of Technical Staff

About MentisAt Mentis, we are dedicated to creating reliable AI solutions for critical sectors such as finance, healthcare, and legal. Our team specializes in developing meticulously curated evaluation datasets and reinforcement learning environments. We empower AI labs and startups by providing them with expertly crafted training data, calibrated assessment rubrics, and rigorous task environments to push the boundaries of AI capabilities in regulated industries.As a tight-knit team based in London, we pride ourselves on our agility and commitment to excellence. Every member plays a vital role in our mission, and we value initiative and ownership in our collaborative work culture. If you are passionate about shaping the future of frontier AI applications, we want to hear from you.About the RoleAs a Software Engineer and Member of Technical Staff, you will be instrumental in building and scaling the platform that drives Mentis' operations. You will develop essential annotation tools, workflow systems, quality control pipelines, and internal infrastructure fundamental to every dataset and environment we deliver.Your daily tasks will include designing expert task creation workflows, creating task assignment and review interfaces, developing data pipelines to convert expert outputs into structured training sets, and integrating LLM-powered tools into our product. Your role will vary from product engineering to infrastructure development, with a consistent focus on producing high-quality evaluation data at scale.You will take ownership of the platform's development, making key decisions on what features to build, how to implement them, and establishing the standards for our growth.What You'll DoDevelop and manage the core data annotation and workflow platform from start to finish, overseeing task assignment, expert interfaces, quality control, and dataset delivery.Design systems that facilitate expert onboarding, task routing, review workflows, and scalable quality assurance processes.Enhance AI-integrated pipelines across the platform, including LLM-assisted annotation, automated checks, and model-in-the-loop workflows.Collaborate directly with founders and domain experts to streamline bespoke processes into effective, scalable software solutions.Make informed product and engineering decisions in a dynamic environment, prioritizing and shipping features without waiting for perfect specifications.Contribute to defining our team’s development practices, including tooling choices, engineering standards, and product strategy.Who We're Looking ForWe seek a proactive individual who thrives in fast-paced environments and embraces ambiguity. If you are excited about the opportunity to influence how AI learns and operates in real-world settings, we welcome your application.

About OpenCoreOSA High-Performance Ledger: We deliver an ultra-efficient ledger built on Go, Rust, and multi-region distributed databases, providing banks with a robust, adaptable, and open framework for development, rather than a restrictive monolithic structure.AI-Integrated Solutions: AI is not merely an enhancement; it's an integral aspect of our system architecture. We leverage AI to facilitate autonomous operations, create dynamic development workflows, and establish a self-optimizing platform.Reliability and Openness: Our focus is on achieving five-nines reliability and unwavering consistency, designed to support Tier-1 banks that handle hundreds of millions of transactions daily. By utilizing open technologies and forging new standards, we promote innovation without imposing lock-in constraints.Leadership with Proven Expertise: Our leadership team merges the strategic vision of former McKinsey banking, product, and engineering specialists with the real-world experience of a founder who developed and scaled a mission-critical fintech solution for the world's largest banks. This is complemented by insights from ex-global bank CIOs, providing us with an unmatched understanding of the evolving market landscape.Your RoleLedger Engine: Develop a deterministic, event-sourced transaction engine.Interest & Pricing Engine: Perform high-precision financial calculations.Reconciliation Engine: Ensure invariants, controls, and cross-ledger consistency.Operational Data Store (ODS): Manage a real-time operational data plane.Scalability Layer: Address concurrency, throughput, partitioning, and replication challenges.AI-Driven Development Experience: Work with MCP servers, agent workflows, and automated runbooks.Your Key ResponsibilitiesCreate initial MVPs for Tier-1 banks.Design distributed systems leveraging Go, Kafka, and distributed SQL databases.Manage systems throughout the entire SDLC (coding, testing, DevOps, infrastructure, product development).Implement advanced CI/CD practices and testing automation.

About ApturaAptura is at the forefront of building reliable AI systems through expertly crafted evaluation datasets and reinforcement learning environments. Our mission is to create robust training data and verifiable task environments in high-stakes industries such as finance, healthcare, and legal. We are a dynamic, small team based in London, dedicated to making significant contributions and innovating quickly. Each team member plays a pivotal role, and we value initiative and ownership. If you're passionate about shaping the future of AI in real-world applications, we want to hear from you.About the RoleAs a Member of the Technical Staff within our Software Engineering team, you will develop the platform that supports Aptura’s operations and scalability. Your responsibilities will encompass the creation of annotation tools, workflow systems, quality control pipelines, and the internal infrastructure that underpins every dataset and environment we produce.Your daily tasks will include designing expert task creation flows, developing task assignment and review interfaces, constructing data pipelines to convert expert outputs into structured training datasets, and integrating LLM-powered tools directly into our product. Your work will span product engineering and infrastructure, ensuring that the software you develop enables our small team to deliver high-quality evaluation data at scale.You will be instrumental in bringing our platform vision to life, determining what features to build and how to build them, while establishing our development standards as we expand.What You'll DoTake ownership of the core data annotation and workflow platform from task assignment to dataset delivery.Create systems that facilitate expert onboarding, task routing, review workflows, and quality assurance at scale.Enhance AI-integrated pipelines across the platform, including LLM-assisted annotation and automated checks.Collaborate directly with founders and domain experts to transform manual processes into scalable software solutions.Make informed product and engineering decisions in fast-paced, ambiguous environments, prioritizing effectively and shipping products without waiting for perfect specifications.Contribute to defining our team’s approach to development, including tooling, engineering practices, and product strategy.Who We're Looking ForWe seek a proactive individual who excels in ambiguous environments and thrives on the challenge of defining projects without strict specifications. If you enjoy problem-solving and have a strong foundation in software engineering, you will fit well within our team.

Tessl is an innovative Series A startup headquartered in London, founded by the visionary Guy Podjarny. With over $100M raised from esteemed investors such as Index Ventures, Accel, GV, and Boldstart, we have been recognized among the top players in the industry, ranking #2 in Sifted EU’s B2B SaaS Rising 100 and #20 in Sifted's AI 100 this year.At Tessl, we are on a mission to redefine software development through the power of AI. Our AI Native Developers are pioneering a new approach, defining features, architecture, and workflows through specifications rather than code, effectively guiding the work of AI agents. We are at the forefront of creating a groundbreaking platform that embodies this transformative vision, leading a developer movement and ecosystem.Joining Tessl means becoming an integral part of an early-stage team where you have the chance to influence the future of software creation and maintenance.

Join xai as a Technical Staff Member focusing on Model Training. In this role, you will collaborate with a talented team to develop and optimize machine learning models that drive innovative solutions. Your expertise will contribute to enhancing the performance of our systems and delivering impactful results.

Join Cohere as a valued member of our technical staff, focusing on the safety of our agents. In this critical role, you will be responsible for designing, implementing, and maintaining safety protocols that ensure the integrity and security of our systems. Collaborate with cross-functional teams to develop innovative solutions that enhance agent safety and improve operational efficiency.

Join OpenCoreOS as a Systems Engineer!At OpenCoreOS, we redefine banking technology with our innovative, hyper-performant ledger solutions. Utilizing cutting-edge programming languages like Go and Rust, along with multi-region distributed databases, we empower financial institutions to build on a robust, open foundation instead of a cumbersome monolithic structure.Why Choose Us?Designed for AI: AI isn't just an add-on; it's integrated into our operations, enhancing autonomous workflows and creating intelligent, self-healing systems.Unyielding Reliability: We aim for five-nines reliability to ensure our platform can handle the scale of Tier-1 banks, managing millions of daily transactions without compromising consistency.Industry Expertise: Our leadership team merges strategic insights from seasoned banking professionals with practical experience, ensuring we understand the market dynamics we are transforming.Your Role:Core Financial Systems: Develop mission-critical services ensuring accurate value recording and transfer.Transaction Processing: Create reliable transaction flows that maintain integrity during retries and partial failures.Performance Optimization: Profile and enhance key pathways to ensure predictable latency and scalable throughput.Reliability & Observability: Advance metrics, tracing, logging, and incident readiness for our production systems.AI-Enhanced Development: Utilize and refine AI-driven workflows for improved debugging, operations, and developer efficiency.Core Responsibilities:Manage production systems from start to finish.Enforce safety and correctness through rigorous testing and change management.Troubleshoot distributed and system-level challenges (concurrency, performance, data consistency).

About xAIAt xAI, we are dedicated to developing AI systems that possess a profound understanding of the universe, ultimately assisting humanity in its quest for knowledge. Our compact team is driven, motivated, and committed to engineering excellence, making our organization ideal for individuals who relish challenges and foster curiosity. We pride ourselves on a flat organizational structure where every employee plays a vital role in advancing our mission. We recognize initiative and excellence in our leadership approach, and emphasize the importance of work ethic and prioritization skills. Strong communication abilities are crucial, enabling team members to share knowledge clearly and effectively.About the RoleThis newly established civilian team is focused on engineering and deploying xAI's AI capabilities (models, APIs, tools, and integrations) for international government agencies, regional and local administrations, and public sector workflows globally. We are building the bridge to responsible, impactful AI adoption. Team members will have opportunities for travel and international assignments, primarily in the Americas, Asia, and the Middle East. You will collaborate closely with product, research, infrastructure, and legal/governance teams to ensure that Grok and future models serve global civilian missions effectively while maintaining safety, transparency, and ethical standards.ResponsibilitiesDesign, build, and optimize integrations between xAI's frontier models (e.g., Grok family) and international government systems, platforms, and data environments.Develop secure, scalable solutions for applications such as policy analysis, educational technology, scientific research support, public health modeling, regulatory workflows, and citizen-facing services across diverse global contexts.Collaborate on custom SDKs, APIs, developer tools, and documentation tailored for international government and enterprise developers.Engage with international agency stakeholders to understand requirements, prototype solutions, and iterate based on feedback.

Who are we?At Cohere, we are committed to harnessing intelligence to benefit humanity. Our mission focuses on training and deploying advanced models for developers and enterprises, empowering the creation of innovative AI systems that drive exceptional experiences in areas like content generation, semantic search, retrieval-augmented generation (RAG), and intelligent agents. We believe our contributions are vital for the widespread integration of AI technologies.We take immense pride in our creations. Each team member is empowered to enhance the capabilities of our models and the value they deliver to our clients. We thrive in a fast-paced environment and prioritize actions that best serve our customers.Cohere comprises a talented team of researchers, engineers, designers, and other specialists who are dedicated to their craft. Our diverse perspectives are crucial for developing exceptional products.Join us in shaping the future of AI!Why is this role important?In this position, you will push the boundaries of model post-training, deploying state-of-the-art models into production while bridging the divide between research and real-world application. With one of the highest compute-to-engineer ratios globally, we foster collaboration between engineering and research, allowing everyone to contribute to production code and support research initiatives based on their interests and organizational needs. You will have access to the resources you need to excel.Please note: We have offices in London, Paris, Toronto, San Francisco, and New York, but we also support a remote-friendly work culture!As a Technical Staff Member, your responsibilities will include:Developing and implementing high-performance, scalable software for model training.Consistently performing post-training of models to achieve state-of-the-art performance.Collaborating with specialized teams (Agentic, Code, etc.) to create models with comprehensive performance metrics.Designing and executing strategies to enhance performance and outcomes during training cycles, including supervised fine-tuning (SFT) and reinforcement learning (RL).Conducting research and experimentation using our advanced supercomputing and data infrastructures.Learning from and collaborating with leading researchers in the AI field.Ideal candidates will possess:Exceptional software engineering capabilities.A strong understanding of machine learning frameworks and tools.Experience in collaborative development and version control systems.A passion for continuous learning and applying innovative solutions.

Tessl is an innovative Series A startup situated in London, co-founded by Guy Podjarny. We have successfully raised over $100M from prestigious investors such as Index Ventures, Accel, GV, and Boldstart. This year, we proudly secured the #2 spot in Sifted EU’s B2B SaaS Rising 100 and ranked #20 in Sifted's AI 100.At Tessl, we are on the forefront of revolutionizing software development through AI. AI Native Developers will articulate features, architecture, and workflows through specifications rather than code, guiding the efforts of AI agents. We are crafting the groundbreaking platform for this new paradigm, championing the developer movement and ecosystem around it.Becoming a part of Tessl means joining an early-stage team where you can influence the future of software creation and maintenance.Role OverviewBecome a vital member of our engineering team as we innovate real-time AI Native workflows, tools, and interfaces that will transform how developers build and maintain software.In your role as a Software Engineer, you will possess versatility and independence, eager to engage with cutting-edge AI technology to produce exceptional products. We prioritize speed while ensuring collaboration and thoughtful execution. You will work closely with product, design, and the larger Engineering team to actualize AI Native development in a dynamic, high-trust environment.Your ResponsibilitiesAt Tessl, each day presents new challenges! You will enjoy a significant degree of autonomy, empowering you to make decisions that drive successful outcomes. Here’s a snapshot of your responsibilities:Design and implement new features in collaboration with the product team.Create proofs of concept for innovative ideas you wish to explore.Rapidly prototype new language integrations for our code generation pipeline, followed by a scalable implementation plan.Collaborate with designers to enhance user interactions across the UI, CLI, or existing AI coding agents, ensuring a seamless user experience.Integrate third-party services, such as notification systems, to concentrate on Tessl’s core capabilities.Work with cross-functional teams to architect a solution that fosters collaboration across the platform.Establish an end-to-end testing strategy to boost our confidence in deploying new features.

Who are we?At Cohere, our mission is to harness and scale intelligence for the betterment of humanity. We are dedicated to training and deploying cutting-edge models that empower developers and enterprises to create astonishing AI-driven experiences such as content generation, semantic search, retrieval-augmented generation (RAG), and intelligent agents. We believe that our innovations play a crucial role in the mainstream adoption of AI technologies.We take great pride in the products we develop. Every team member contributes to enhancing our models' capabilities and the value they deliver to our customers. Our culture is driven by hard work and a commitment to swift execution that prioritizes our clients' needs.Cohere is composed of a diverse team of researchers, engineers, designers, and more, all of whom are passionate about their respective fields. Each individual is among the best globally in their area of expertise. We firmly believe that a wide array of perspectives is essential for creating outstanding products.Join us in our quest to shape the future of AI!Why this role?As a Performance Engineer within our Pre-Training team, you will play a pivotal role in optimizing the efficiency and performance of our advanced language models and systems. Your primary focus will be on enhancing critical model training metrics, including training throughput and maximizing accelerator utilization.This team merges software engineering, machine learning, and low-level kernel design expertise to develop robust systems that elevate model performance. You will actively identify and eliminate performance bottlenecks, while also creating innovative training and profiling tools that support Cohere's mission of delivering efficient and reliable language understanding and generation capabilities, thereby driving advancements in natural language processing.Note: While we have offices in London, Toronto, New York, and San Francisco, we are also remote-friendly! This team primarily operates between Eastern Time (ET) and Central European Time (CET), so we are looking for candidates in locations aligned with these time zones for effective collaboration.As a Technical Staff Member, your responsibilities will include:Crafting and developing high-performance, scalable software solutions for model training.Comprehending architectural modifications and design choices and their impacts on training throughput and quality.Writing low-level CUDA and Triton kernels to maximize performance from our accelerators.Conducting research, implementation, and experimentation on our supercomputing and data infrastructure.Collaborating with and learning from top researchers in the field.

Join Our TeamLatent Labs is on the lookout for a talented Machine Learning Research Engineer with extensive expertise in training and deploying large-scale generative models. In this pivotal role, you will oversee our high-performance computing infrastructure and drive our model serving initiatives. You will collaborate with a diverse team of machine learning experts, protein engineers, and biologists, all dedicated to transforming how we manipulate biological systems and develop innovative treatments for diseases.About Latent LabsAt Latent Labs, we are pioneers in creating advanced models that grasp the core principles of biology. Our team, which once co-developed DeepMind's groundbreaking AlphaFold and invented latent diffusion, is committed to scientific rigor and ambitious exploration. By joining us, you will work alongside some of the most brilliant minds in the fields of generative AI and biology, fostering a culture of collaboration and continuous learning between our London and San Francisco offices.We seek innovators who are passionate about solving complex problems and making a positive impact on the world. Be a part of our ambitious mission!

About the Role XAI is hiring a Member of Technical Staff for the X Money team in London. This role focuses on building and improving financial technology products that support the company's mission. What You Will Do Design, develop, test, and deploy software features for the X Money platform Work closely with engineers and other professionals to deliver reliable and secure solutions Help ensure the platform meets standards for performance, scalability, and security Who We’re Looking For Technical staff with a strong interest in financial technology Comfortable taking on challenging projects and collaborating with others Ready to contribute ideas and take ownership of solutions Location This position is based in London, UK.

About UsAt Cohere, we are on a mission to expand intelligence in a way that benefits humanity. We specialize in training and deploying advanced models for developers and enterprises aiming to create AI systems that deliver extraordinary experiences, including content generation, semantic search, retrieval-augmented generation (RAG), and intelligent agents. We are committed to fostering the widespread adoption of AI technology.We take immense pride in what we create. Each team member plays a vital role in enhancing the capabilities of our models and the value they provide to our customers. We thrive in a fast-paced environment where hard work and customer-centricity lead our decisions.Cohere comprises a dynamic group of researchers, engineers, designers, and creatives who are passionate about their work. Our team members are among the best in their fields, and we believe that diverse perspectives are essential for crafting exceptional products.Join us in shaping the future of AI!Why This Role is ExcitingAs a Member of Technical Staff at Cohere, you will be pivotal in defining and developing the future of AI-driven products. This role provides you with the opportunity to convert groundbreaking research into high-performance products that propel our enterprise forward. You will work directly on North, our comprehensive and secure AI workspace platform, focusing on agent development in RAG, tool utilization, and language agents.We boast one of the highest compute-to-engineer ratios globally, offering an environment where your ideas can thrive and be swiftly brought to market.Please note: We have offices in London, Paris, Toronto, San Francisco, and New York. However, we also support remote work within EMEA-friendly time zones. Our team primarily operates between ET and CET, so we are looking for candidates in locations that align with these hours for effective collaboration.As a Member of Technical Staff, your responsibilities will include:Collaborating with a diverse team of engineers to design, build, and scale AI systems that form the backbone of our suite of developer-centric enterprise products.Contributing directly to North, our all-in-one secure AI workspace platform, where you will lead agent development in RAG, tool usage, and language agents.Rapidly researching and experimenting with innovative ideas on our advanced supercomputer and data infrastructure to keep our products at the cutting edge of the industry.Partnering with leading researchers, engineers, and annotators to generate and evaluate data for post-training large language models (LLMs), ensuring our products are top-notch.

Join Our Team as a Staff Software EngineerAt Deliveroo, we are dedicated to revolutionizing the way people shop and dine. Our commitment to impact, innovation, and growth is at the core of everything we do. Our engineering teams are tasked with addressing intricate technical challenges within a global, three-sided marketplace, developing and scaling systems that cater to millions of customers, riders, and partners daily.From real-time logistics to robust infrastructure and marketplace optimization, we design, build, and operate the technology that fuels Deliveroo's expansive growth.We are seeking a Staff Software Engineer to become a key member of our London, UK - Hybrid (3 days in the office) team. In this pivotal role, you will help us craft technical solutions for essential business challenges and steer the technical direction for complex, high-scale systems.Discover our Engineering team — learn about our motivations, work culture, and what you can expect when you join us.

Join our dynamic team as a Staff Software Engineer at CyberArk, where you will be instrumental in developing cutting-edge security solutions. You will collaborate with a talented group of engineers to design, implement, and maintain software systems that protect against evolving cyber threats. Your expertise will contribute to innovative projects that shape the future of enterprise security.

Join unlikelyAI as a Staff Software Engineer and be at the forefront of developing cutting-edge artificial intelligence solutions. In this pivotal role, you will collaborate with a talented team to design, implement, and optimize software systems that push the boundaries of technology.As a key member of our engineering team, you'll have the opportunity to influence the architecture of our products and mentor junior engineers. We are looking for innovative thinkers who thrive in a fast-paced environment and are passionate about building scalable and efficient software.

About xAIAt xAI, we are on a mission to develop advanced AI systems that deeply comprehend the intricacies of the universe while assisting humanity in its quest for knowledge. Our team is compact, highly driven, and dedicated to engineering excellence. We are looking for individuals who embrace challenges and thrive on curiosity. Operating with a flat organizational structure, we encourage all employees to be proactive and contribute directly to our mission. Leadership is awarded to those who demonstrate initiative and consistently achieve high standards. A strong work ethic and effective prioritization skills are essential. Excellent communication skills are expected, enabling team members to share knowledge clearly and concisely.About the PositionAs a Technical Staff Member, you will be responsible for developing frameworks to enhance reasoning capabilities, constructing distributed reinforcement learning systems, and implementing inference time computation techniques (such as tree search and planning). You will also create environments for agents, gaining exposure to a wide range of components across the entire technical stack.Tech StackPythonJAXRustFocus AreasDevelop robust and scalable distributed reinforcement learning systems.Optimize frameworks for complex inference-time reasoning tasks.

Join Plaid as a Staff Software Engineer and be a vital part of our team in London. We are looking for innovative engineers who are passionate about building the infrastructure that powers the future of fintech. You will work alongside talented professionals, contributing to an exciting array of projects that will challenge your skills and help you grow.

About Checkout.com Checkout.com helps businesses succeed in the digital economy. Leading companies such as eBay, ASOS, Klarna, Uber Eats, and Sony rely on our platform to process seamless online payments. Our global network supports billions of transactions each year, focusing on reliability and ease of use. Headquartered in London, Checkout.com operates from 19 offices across six continents. The company values high performance and continuous improvement. Working here means contributing to the future of fintech alongside teams striving for excellence. Role Overview: Staff Software Engineer - Streaming The Data and AI Platform Team is looking for a Staff Software Engineer to help build a scalable platform for AI-driven streaming and batch data applications. This platform will improve how data is shared and used across Checkout.com, supporting business growth and performance. The team’s mission is to make it easier for internal teams to collect, store, process, and use data for impactful AI projects and data products. The focus is on reducing technical overhead so engineers can spend more time solving business challenges, not managing infrastructure or deployments. Current work lays the foundation for systems that will scale to support hundreds of teams and handle petabytes of data. Main Responsibilities Design and develop a highly available event streaming platform using technologies like Kafka and Flink. Offer technical leadership and mentorship, providing strategic direction and building strong relationships with engineers and managers across the organization. Work with cross-functional teams to deliver data solutions that support business goals. Location This role is based in London.