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Machine Learning Scientist / Engineer - LLM, NLP & Model Training

Location: Seattle, WA - Onsite
Engagement: Contract
Start: November 2026

Are you an experienced Machine Learning Engineer, ML Scientist, NLP Scientist, Research Scientist, or Applied Scientist who has personally trained and improved machine learning models?

We're looking for an ML professional to help develop production GenAI solutions supporting multilingual content across text, images, and video.

Your current title matters less than the work you've actually done.

We're particularly interested in people who can answer questions like:

Why isn't this model performing well?What changes should we make to the training data or fine-tuning strategy?Which foundation model is best suited to this problem?How do we objectively demonstrate that the new model performs better?How do we take the resulting model into a real production environment?What We're Looking For

You should have direct experience with several of the following:

Fine-tuning LLMs or transformer modelsTraining ML/NLP modelsLoRA / QLoRA / PEFTHugging Face / PyTorchInstruction tuning or domain adaptationBuilding or curating training datasetsModel evaluation and benchmarkingHyperparameter optimizationNLP / language modelingMachine translationMultilingual modelsOCR / image understandingVision-language or multimodal modelsProduction model deploymentModel hosting and inference

This is not primarily an MLOps, infrastructure, prompt-engineering, or AI-agent development position. The core work involves choosing, training, fine-tuning, evaluating, and improving the models themselves, while partnering with an established MLOps function on production infrastructure. The official role specifically requires LLM experience beyond prompt engineering and direct work with model internals. Applied_Scientist_GenAI_LLM_Tra…

Background

Successful candidates will generally bring:

3+ years building ML models for real-world applications.Strong hands-on model training/fine-tuning experience.Experience taking ML models into production.Strong Python skills.Understanding of modern foundation-model architectures and training techniques.Ability to independently investigate model failures, design experiments, and improve performance.PhD OR Master's degree plus 4+ years of relevant experience in Computer Science, Machine Learning, Computer Engineering, or a related field. Applied_Scientist_GenAI_LLM_Tra…

Experience in NLP, machine translation, multilingual ML, OCR, or vision-language models is particularly valuable. Applied_Scientist_GenAI_LLM_Tra…

This is an opportunity to work on ML systems processing millions of pieces of content per day across 130+ locales, solving problems where off-the-shelf models are not sufficient. Applied_Scientist_GenAI_LLM_Tra…

Location: Seattle, WA - onsite five days/week.

GCS is acting as an Employment Business in relation to this vacancy.

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Applied Scientist - GenAI / LLM & Machine Translation

Location: Seattle, WA - Onsite 5 days/week
Engagement: Contract
Start: November 2026

We are seeking an experienced Applied Scientist to join a newly established science team focused on developing and deploying next-generation LLM, NLP, and multimodal machine learning solutions at significant production scale.

This is a hands-on applied science position for someone who has personally trained and fine-tuned machine learning models, understands how foundation models work internally, and can take models from experimentation through production deployment.

The team is developing GenAI solutions supporting large-scale multilingual content and translation workflows across text, images, and video. The environment has a start-up mentality with significant opportunity to influence model selection, experimentation, and technical direction. Applied_Scientist_GenAI_LLM_Tra…

What You'll DoFine-tune LLMs and transformer-based models for production applications.Design and execute model-training and evaluation experiments.Build and prepare datasets for model training and fine-tuning.Evaluate model performance, identify failure modes, and determine how to improve accuracy and quality.Select appropriate foundation models and model sizes based on the problem.Work across NLP, machine translation, OCR, image localization, and multimodal ML workflows.Deploy production-grade models operating at large scale and low latency.Partner with MLOps and engineering teams to automate training, inference, sampling, and deployment workflows.Communicate experimental results and technical recommendations to technical and non-technical stakeholders. Applied_Scientist_GenAI_LLM_Tra…Required Qualifications3+ years of experience building machine learning models for real-world business applications.Demonstrated hands-on experience fine-tuning LLMs or transformer-based models, beyond prompt engineering or API integration.Experience modifying model weights, parameters, hyperparameters, training approaches, or model architectures.Strong understanding of foundation models and modern ML/model-training concepts.Experience evaluating model performance and using experimental results to improve models.Experience deploying machine learning models into production environments.Strong Python programming skills.PhD OR Master's degree plus 4+ years of relevant experience in Computer Science, Machine Learning, Computer Engineering, or a related field. Applied_Scientist_GenAI_LLM_Tra…Highly Desired

Experience with technologies or domains such as:

Llama | Mistral | T5/mT5 | NLLB | PyTorch | Hugging Face | LoRA | QLoRA | PEFT | NLP | Machine Translation | Multilingual NLP | OCR | Vision-Language Models

Experience hosting or serving models and publications or patents in relevant ML disciplines are also valuable. Applied_Scientist_GenAI_LLM_Tra…

Location Requirement: This position is onsite in Seattle, WA five days per week. Candidates willing to relocate are welcome and should be prepared to relocate at their own expense. Former Amazon employees are welcome to apply.

GCS is acting as an Employment Business in relation to this vacancy.

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Key ResponsibilitiesDesign, develop, test, deploy, and operate production-grade security automation and AI-driven workflows.Build intelligent agents capable of securely accessing security data, invoking approved tools, maintaining context, and executing multi-step workflows.Develop automation that can assist with:Threat intelligenceThreat huntingDetection engineeringSecurity investigationsIncident responseSecurity data analysisApply modern AI and automation techniques, including:Tool callingRetrieval-augmented generation (RAG)Structured generationPlanningReflectionVerificationModel routingMulti-agent coordinationDesign mechanisms for memory, context management, task recovery, escalation, and human approval.Build automation designed to reduce operational noise and false positives while improving the speed and consistency of security response.Develop appropriate security controls and guardrails around AI agents and automated workflows.Create evaluation and testing strategies to measure the accuracy, reliability, security, and performance of automation.Evaluate emerging AI models, agent frameworks, automation platforms, and orchestration technologies.Prototype new capabilities and transition successful solutions into reliable production environments.Work closely with threat intelligence analysts, threat hunters, detection engineers, incident responders, and security-data engineers to understand operational challenges.Translate security requirements and operational processes into scalable technical solutions.Develop clean, maintainable, scalable, and well-documented code.Troubleshoot, monitor, and continuously improve automation running in production.Participate in architecture, design, code reviews, and technical decision-making.Identify opportunities to automate repetitive or time-sensitive security processes and improve overall SOC efficiency.Required QualificationsBachelor's degree in Computer Science, Engineering, Cybersecurity, Information Systems, or a related field, or equivalent professional experience.8+ years of experience in software engineering, security engineering, automation engineering, AI/ML engineering, or a related technical field.Strong hands-on software development experience.Experience building automation solutions or AI-powered applications for production environments.Experience working with Large Language Models (LLMs), generative AI, or agentic AI technologies.Strong programming skills in Python and/or another modern programming language.Experience integrating applications with APIs, tools, data sources, and external systems.Understanding of AI agent concepts such as tool use, planning, context management, retrieval, memory, and verification.Experience designing and implementing reliable, scalable technical solutions.Strong analytical and problem-solving skills.Ability to work with both software engineers and security professionals to translate operational challenges into technical solutions.Preferred QualificationsExperience building agentic AI systems or autonomous security workflows.Experience with security automation, SOAR, SIEM, or security orchestration platforms.Experience with cybersecurity operations, threat intelligence, threat hunting, detection engineering, or incident response.Experience with RAG, vector databases, embeddings, semantic search, or knowledge retrieval.Experience with multi-agent architectures and AI orchestration frameworks.Experience developing AI evaluation frameworks, testing harnesses, or benchmarking processes.Experience with Kubernetes, cloud platforms, microservices, APIs, and distributed systems.Experience implementing human-in-the-loop controls and approval workflows.Experience taking AI/automation solutions from proof of concept through production deployment.Familiarity with security controls and best practices for deploying AI systems in enterprise environments.

GCS is acting as an Employment Business in relation to this vacancy.

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Job Summary

We are looking for a Full Stack Engineer with strong experience in React.js, backend development, AWS, microservices, and Kubernetes. The ideal candidate will work closely with Product, UX, and Engineering teams to build scalable, high-performance applications and services.

Key ResponsibilitiesDesign and develop scalable frontend applications using React.js.Develop backend APIs and services using Node.js, Golang, and/or Python.Build and maintain microservices and distributed systems.Develop and deploy cloud-based applications using AWS.Work with Docker and Kubernetes for containerization and orchestration.Collaborate with Product Managers, UX Designers, and Engineers to deliver new features.Ensure seamless frontend and backend integration with a focus on performance and reliability.Participate in code reviews, testing, debugging, and CI/CD automation.Document technical designs, APIs, and workflows.Work closely with UX designers to ensure implementations match the intended user experience.Required SkillsStrong experience with React.js and full-stack development.Hands-on experience with Node.js, Golang, and/or Python.Experience with AWS, Kubernetes, Docker, and CI/CD.Strong understanding of REST APIs, microservices, and distributed systems.Good problem-solving and communication skills.Preferred ExperienceExperience with live video platforms and video editing tools.Experience building LLM agents and MCP-based solutions.Strong experience with Golang.Production experience with Kubernetes.

GCS is acting as an Employment Business in relation to this vacancy.

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Job Summary

We are looking for a Full Stack Engineer with strong experience in React.js, backend development, AWS, microservices, and Kubernetes. The ideal candidate will work closely with Product, UX, and Engineering teams to build scalable, high-performance applications and services.

Key ResponsibilitiesDesign and develop scalable frontend applications using React.js.Develop backend APIs and services using Node.js, Golang, and/or Python.Build and maintain microservices and distributed systems.Develop and deploy cloud-based applications using AWS.Work with Docker and Kubernetes for containerization and orchestration.Collaborate with Product Managers, UX Designers, and Engineers to deliver new features.Ensure seamless frontend and backend integration with a focus on performance and reliability.Participate in code reviews, testing, debugging, and CI/CD automation.Document technical designs, APIs, and workflows.Work closely with UX designers to ensure implementations match the intended user experience.Required SkillsStrong experience with React.js and full-stack development.Hands-on experience with Node.js, Golang, and/or Python.Experience with AWS, Kubernetes, Docker, and CI/CD.Strong understanding of REST APIs, microservices, and distributed systems.Good problem-solving and communication skills.Preferred ExperienceExperience with live video platforms and video editing tools.Experience building LLM agents and MCP-based solutions.Strong experience with Golang.Production experience with Kubernetes.

GCS is acting as an Employment Business in relation to this vacancy.

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Job Summary

We are looking for a Full Stack Engineer with strong experience in React.js, backend development, AWS, microservices, and Kubernetes. The ideal candidate will work closely with Product, UX, and Engineering teams to build scalable, high-performance applications and services.

Key ResponsibilitiesDesign and develop scalable frontend applications using React.js.Develop backend APIs and services using Node.js, Golang, and/or Python.Build and maintain microservices and distributed systems.Develop and deploy cloud-based applications using AWS.Work with Docker and Kubernetes for containerization and orchestration.Collaborate with Product Managers, UX Designers, and Engineers to deliver new features.Ensure seamless frontend and backend integration with a focus on performance and reliability.Participate in code reviews, testing, debugging, and CI/CD automation.Document technical designs, APIs, and workflows.Work closely with UX designers to ensure implementations match the intended user experience.Required SkillsStrong experience with React.js and full-stack development.Hands-on experience with Node.js, Golang, and/or Python.Experience with AWS, Kubernetes, Docker, and CI/CD.Strong understanding of REST APIs, microservices, and distributed systems.Good problem-solving and communication skills.Preferred ExperienceExperience with live video platforms and video editing tools.Experience building LLM agents and MCP-based solutions.Strong experience with Golang.Production experience with Kubernetes.

GCS is acting as an Employment Business in relation to this vacancy.

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Senior Full-Stack Developer

Location: Hybrid (East - Flanders)
Employment Type: Full-Time

About the Opportunity

We're partnering with an ambitious, technology-driven organisation that is building a modern, scalable digital platform with significant growth plans. As the business continues to expand, we're seeking a Senior Full-Stack Developer to take ownership of a key product and play a central role in shaping its technical direction.

This is an exciting opportunity for an experienced developer who enjoys combining technical ownership with hands-on development. You will play a pivotal role in architectural decisions, product evolution, and the growth of the engineering function.

Key Responsibilities

Design, build, and enhance core product features across the full technology stack.Contribute to architectural decisions and technical strategy to ensure scalability and maintainability.Collaborate with product, engineering, and business stakeholders to deliver impactful solutions.Champion engineering best practices, quality standards, and modern development approaches.Leverage AI-powered tools and emerging technologies to improve development efficiency and outcomes.Support the growth and maturity of the engineering function through technical leadership and knowledge sharing.

What We're Looking For

6+ years' professional software engineering experience.Strong JavaScript and TypeScript expertise.Proven experience balancing hands-on development with architectural decision-making.Experience with cloud platforms such as AWS, Azure, or GCP.Experience building modern web applications using Node.js (NestJS) and React or Next.js.Familiarity with Docker, CI/CD, and modern DevOps practices.Experience with PostgreSQL or other relational databases.Strong communication, stakeholder management, and problem-solving skills.Enthusiasm for AI-powered development tools and emerging technologies.

Why This Opportunity?

This is an opportunity to join a growing organisation where you'll have genuine ownership, influence, and impact. You'll work on a modern technology platform, help shape technical direction, and play a key role in the next stage of product growth.

If you're a senior Developer who enjoys solving complex challenges, taking ownership, and building scalable products in a collaborative environment, we'd love to hear from you.

GCS is acting as an Employment Agency in relation to this vacancy.

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Web UI Developer

We are looking for a talented Web UI Developer to join our team and help create high-quality, engaging digital experiences for our customers.

In this role, you will work closely with designers, developers, QA teams, and project stakeholders to transform designs and business requirements into responsive, functional, and visually polished web experiences. You'll contribute throughout the development lifecycle-from design implementation and development through testing, optimization, and ongoing maintenance.

This is an excellent opportunity for an early-career developer who is passionate about front-end technologies, enjoys solving problems, and takes pride in creating exceptional user experiences.

What You'll Do

Convert UI and visual designs into clean, responsive, and pixel-perfect web experiences using HTML, CSS, and JavaScript.

Develop and maintain customer-facing websites, features, and digital experiences.

Collaborate with designers and project teams to ensure designs are accurately implemented.

Build new front-end features and enhance existing functionality.

Support website redesign, enhancement, and maintenance initiatives.

Work with a variety of CMS, eCommerce platforms, frameworks, and third-party tools.

Configure and manage plugins and integrations needed to support website functionality.

Participate in design, development, testing, QA, and release activities.

Troubleshoot technical issues, identify root causes, and implement fixes.

Ensure applications are optimized for performance, responsiveness, scalability, and usability.

Validate user input and support secure communication between front-end and back-end systems.

Participate in code reviews and contribute to coding standards and development best practices.

Identify project blockers and work collaboratively to develop creative solutions.

Stay current with evolving front-end technologies, tools, and industry trends.

What You'll Bring

Bachelor's degree in Computer Science, Web Development, Information Technology, or a related field, or equivalent practical experience.

Approximately 1-3 years of experience in web, UI, or front-end development.

Strong knowledge of HTML, CSS, and JavaScript.

Experience developing responsive websites and user interfaces.

Familiarity with modern web development practices and browser compatibility.

Experience or exposure to CMS and/or eCommerce platforms.

Understanding of software testing, debugging, and quality assurance practices.

Strong attention to detail, especially when translating visual designs into functional web experiences.

Ability to troubleshoot issues and develop effective solutions.

Strong communication and collaboration skills.

A creative mindset and willingness to learn new technologies.

Preferred Qualifications

Experience with modern JavaScript frameworks or libraries.

Familiarity with content management systems and eCommerce platforms.

Knowledge of responsive design and web accessibility principles.

Experience with Git or other version control tools.

Exposure to performance optimization and web application scalability.

Experience working in an Agile or collaborative development environment.

If you enjoy building polished, user-friendly web experiences and want to work on projects that directly impact how customers interact with a brand, we'd love to hear from you.

GCS is acting as an Employment Business in relation to this vacancy.

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Full Stack Developer (Contract)

Location: Remote (UK)
Contract Length: 6 Months
Day Rate: £400 per day OUTSIDE IR35
Tech Stack: C#, SQL, Vue.js

Overview

We are seeking an experienced Full Stack Developer to support the re-engineering and modernisation of a core business platform. The successful candidate will play a key role in migrating an existing application from .NET Framework 4.1 to .NET 10, helping to improve performance, scalability, maintainability and cloud readiness.

Working within an agile development team, you will contribute across the full software development lifecycle, from architecture and design through to development, testing and deployment.

Key Responsibilities

Redevelopment and modernisation of an existing platform from .NET Framework 4.1 to .NET 10.Design, develop and maintain scalable web applications using C#, SQL Server and Vue.js.Collaborate with business stakeholders, architects and developers to define technical solutions.Refactor legacy code and implement modern development practices.Develop and consume RESTful APIs and backend services.Optimise database performance and maintain SQL Server environments.Participate in code reviews, testing and release activities.

Essential Skills & Experience

Strong commercial experience developing applications using C#.Experience with SQL Server, including:Proven experience developing front-end applications with Vue.js.Experience working on full software development lifecycle projects.Demonstrable experience modernising or upgrading legacy applications.

Desirable Skills

Experience with Microsoft Azure services.Knowledge of Azure DevOps and CI/CD pipelines.Experience containerising applications using Docker and Kubernetes.Experience with microservices architecture.Exposure to Entity Framework Core.

Ideal Candidate

Comfortable working in a fast-paced project environment.Proven track record of delivering platform modernisation projects.Able to work independently whilst collaborating effectively within a wider team.Strong attention to detail with a focus on quality and maintainability.

Technical Environment

.NET Framework 4.1 → .NET 10 MigrationC#SQL ServerVue.jsAzure (desirable)

GCS is acting as an Employment Business in relation to this vacancy.

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Job Description

- Implements, refines, and validates machine learning algorithms for products and applications. - Implements data pipelines consisting of data ingest, data validation, data cleaning, and data monitoring.

- Trains machine learning models, validates the accuracy of the machine learning models once trained, and deploys validated machine learning models into production.

- Assists in development of proof of concept solutions and contributes to studies to support future product or application development.

- Researches, writes, and edits documentation and technical requirements, including evaluation plans, confluence pages, white papers, presentations, test results, technical manuals, formal recommendations, and reports.

- Tests and evaluates solutions. Completes case studies, testing, and reporting.

Skills

- Bachelor's degree in computer science, computer engineering, mathematics, related technical discipline, or related industry experience

- Experience with machine learning, deep learning, data mining, and/or statistical analysis tools and how to deploy and monitor machine learning models.

- Strong programming and software development skills and familiarity with Python, Java or Scala.

- Knowledge of data pipeline and cloud technologies such as Kafka, Spark, and Docker.

- 1-3 years related experience after Bachelors.

GCS is acting as an Employment Business in relation to this vacancy.

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