Senior Software Engineer in City of Westminster

We're looking for a Senior Software Engineer to join one of our Content Management System (CMS) product teams in the UK, working on a key part of the Optimizely platform. Our CMS is one of the core products in the Optimizely ecosystem. It enables businesses to create, manage, and publish digital content—such as websites, landing pages, and product experiences—across multiple channels. It works alongside other parts of the platform, including experimentation, campaign management, and data services, to support end‑to‑end digital experience creation and optimization.

We offer both PaaS and SaaS versions of our CMS and are continuously evolving it to be more scalable, composable, and developer‑friendly. As part of this team, you'll help build and evolve core CMS capabilities while contributing to the long‑term direction of the platform.

About the Team

Our team focuses on building extensible CMS capabilities and integrations that make the platform more flexible and useful for customers. This includes developing add-ons such as:

• Forms – a flexible form‑building capability that allows users to create and manage dynamic forms based on predefined UX layouts, without requiring developer involvement.
• Language Manager – enabling editors to work efficiently with multilingual content.
• AI tools & agents – we are building AI‑powered capabilities to streamline how forms and content experiences are created and managed.

In addition, we integrate the CMS with external systems and services, helping it fit into a wide range of customer architectures. This includes ingesting data from other Optimizely products and enabling seamless data flow into marketing automation systems to support high‑impact campaigns. A significant part of our work involves designing and maintaining REST APIs that expose CMS functionality and enable flexible, composable use of the platform.

Our CMS is not just a product—it's also a platform used and extended by a global developer community. Customers and partners build custom solutions, integrations, and extensions on top of it. Because of that, we place strong emphasis on clean, well‑structured code, clear abstractions, and solid separation of concerns. We aim to provide stable APIs and extension points that make the platform easy to customize and build upon.

You'll be joining a group of experienced engineers with deep product knowledge and diverse technical backgrounds. While engineers on this team are based in Hanoi, Vietnam, the wider CMS organization spans the US, UK, Stockholm, Vietnam, and Bangladesh. We value collaboration, open communication, and shared ownership across these global locations.

We have an office in London and support a hybrid setup. If you're based elsewhere in the UK, we also support fully remote work.

How We Work

We're a global company, and our teams collaborate across time zones while respecting local working hours and personal commitments. We care about work‑life balance in practice. Occasionally, there may be urgent production issues or releases that require extra effort, but this is the exception rather than the norm. Many engineers stay with us long‑term because the work remains interesting and the environment is supportive.

Job Responsibilities

• Design, build, and maintain scalable, maintainable software systems.
• Develop CMS features, add‑ons, APIs, and integrations with external systems.
• Contribute to system design and architectural decisions.
• Ensure product quality through automated testing and operational best practices.
• Own services in production, including monitoring and incident handling.
• Collaborate with product managers, designers, and engineers to deliver features end‑to‑end.
• Consider real‑world usage and customer needs in technical decisions.
• Mentor other engineers and contribute to knowledge sharing.
• Participate in hiring and help grow the engineering team.

Knowledge and Experience

Must have

• ~8+ years of experience in software engineering (flexible depending on experience).
• Strong fundamentals in software design and engineering.
• Experience with C# and .NET, and React on the frontend.
• Experience with CMS platforms, content modelling, or similar domains.
• Experience building and operating cloud‑based systems.
• Comfortable using AI tools (e.g., Claude or similar) in your daily workflow for problem solving, learning, and improving code quality and delivery speed.
• Strong testing mindset, with a focus on building reliable, well‑tested systems and maintaining high code quality.
• Comfortable working in cross‑functional, agile teams.
• Strong communication and collaboration skills.

Nice to have

• Experience with Optimizely CMS or similar CMS/DXP platforms.
• .NET Core / MVC.
• SQL (especially MS SQL).
• REST APIs or GraphQL.
• Containers and cloud platforms (e.g., Azure).
• Experience building modular systems with continuous delivery.
• Experience building AI‑powered features (e.g., RAG systems, LLM integrations).
• Degree in Computer Science or equivalent experience.

Education

Bachelor’s Degree (Computer Science or engineering preferred) or equivalent work experience.

Optimizely is committed to a diverse and inclusive workplace. Optimizely is an equal opportunity employer and does not discriminate on the basis of race, national origin, gender, gender identity, sexual orientation, protected veteran status, disability, age, or other legally protected status.