At a Glance
- Tasks: Design and optimise a high-performance UI framework for real-time applications.
- Company: High-growth software company powering mission-critical applications globally.
- Benefits: Competitive salary, private healthcare, gym membership, and generous holiday allowance.
- Other info: Join a flat-structured, engineering-first culture with excellent career growth.
- Why this job: Shape the future of UI frameworks and tackle unique engineering challenges.
- Qualifications: Mastery of JavaScript/TypeScript with exposure to C++, Java, or C#.
The predicted salary is between 150000 - 200000 £ per year.
Location: London (Hybrid – 2 days WFH)
Salary: £150,000 - £200,000 (Permanent) pension, private healthcare, gym membership, 25 days + 8 BH holiday allowance, tech/hardware budget.
A high-growth software company is building the gold standard in UI frameworks and data-intensive visualisation technology. With millions of weekly downloads and adoption by the world’s largest financial institutions and technology businesses, their product powers mission-critical applications across the Fortune 500.
They are now hiring exceptional engineers who want to work at the edge of what’s possible in the browser — solving problems of scale, speed, and complexity that ordinary web development never touches.
What you’ll do
- Design and optimise a high-performance UI framework used globally in real-time applications.
- Push the limits of JavaScript, TypeScript, and the browser runtime to handle millions of data points smoothly.
- Solve deep algorithmic and architectural challenges in rendering, scalability, and memory efficiency.
- Own features end-to-end: design, code, test, release, and iterate.
- Contribute to a product used by developers and enterprises worldwide.
What you’ll bring
- Mastery of vanilla JavaScript and TypeScript, with additional exposure to C++, Java, or C#.
- Strong knowledge of data structures, algorithms, and performance optimisation.
- Experience with frameworks like React, Angular, or Vue, and a deep understanding of DOM internals and rendering pipelines.
- A systems-level mindset: diagnosing bottlenecks, eliminating memory leaks, optimising rendering and throughput.
- Passion for building scalable, developer-facing libraries and frameworks, not just apps.
Why join?
- Shape the future of UI frameworks at massive scale, tackling problems most engineers never encounter.
- Competitive salary £150,000 – £200,000 plus bonus and benefits.
- Engineering-first culture: flat structure, no bureaucracy, high-calibre peers.
- Hybrid work model: central London office, two days WFH.
- Premium benefits: private healthcare, pension, gym membership, cutting-edge hardware.
If you’re ready to engineer the engines behind some of the world’s most demanding applications, we’d love to hear from you. Apply now and build technology trusted by the Fortune 500.
Principal JavaScript Performance Engineer (with C++ / Java / C# exposure) - London employer: techstack Recruitment
Join a high-growth software company at the forefront of UI frameworks and data visualisation technology, where you'll collaborate with top-tier engineers in a flat, engineering-first culture. Enjoy a competitive salary alongside premium benefits such as private healthcare, gym membership, and a generous holiday allowance, all while working in a hybrid model from a central London office. This is an exceptional opportunity to shape the future of technology used by Fortune 500 companies, offering meaningful challenges and significant growth potential.
StudySmarter Expert Advice🤫
We think this is how you could land Principal JavaScript Performance Engineer (with C++ / Java / C# exposure) - London
✨Tip Number 1
Network like a pro! Reach out to folks in your industry on LinkedIn or at meetups. You never know who might have the inside scoop on job openings or can put in a good word for you.
✨Tip Number 2
Show off your skills! Create a portfolio showcasing your projects, especially those that highlight your JavaScript and performance optimisation expertise. This is your chance to shine and demonstrate what you can bring to the table.
✨Tip Number 3
Prepare for technical interviews by brushing up on algorithms and data structures. Practice coding challenges on platforms like LeetCode or HackerRank. We want you to feel confident when tackling those tricky questions!
✨Tip Number 4
Don’t forget to apply through our website! It’s the best way to ensure your application gets seen by the right people. Plus, we love hearing from passionate engineers ready to make an impact!
We think you need these skills to ace Principal JavaScript Performance Engineer (with C++ / Java / C# exposure) - London
Some tips for your application 🫡
Show Off Your Skills:Make sure to highlight your mastery of JavaScript and TypeScript right from the start. We want to see how you’ve tackled performance optimisation and any cool projects you've worked on that showcase your skills.
Tailor Your Application:Don’t just send a generic CV! Tailor your application to reflect the specific requirements in the job description. Mention your experience with frameworks like React, Angular, or Vue, and how you’ve solved complex problems in the past.
Be Clear and Concise:Keep your application clear and to the point. We appreciate well-structured applications that are easy to read. Use bullet points where necessary to make your achievements stand out!
Apply Through Our Website:We encourage you to apply directly through our website. It’s the best way for us to receive your application and ensures you don’t miss out on any important updates from our team!
How to prepare for a job interview at techstack Recruitment
✨Know Your Tech Inside Out
Make sure you have a solid grasp of JavaScript, TypeScript, and any other languages mentioned like C++, Java, or C#. Brush up on data structures and algorithms, as these will likely come up in technical questions. Being able to discuss your past experiences with performance optimisation will definitely set you apart.
✨Showcase Your Problem-Solving Skills
Prepare to discuss specific challenges you've faced in previous roles, especially those related to rendering, scalability, and memory efficiency. Use the STAR method (Situation, Task, Action, Result) to structure your answers, making it easy for interviewers to see how you tackle complex problems.
✨Familiarise Yourself with Their Product
Do some research on the company’s UI frameworks and data visualisation technology. Understanding their product will not only help you answer questions more effectively but also allow you to ask insightful questions that show your genuine interest in what they do.
✨Prepare for Cultural Fit Questions
Since the company values an engineering-first culture with a flat structure, be ready to discuss how you work in teams and handle feedback. Share examples of how you've contributed to a collaborative environment and how you align with their mission to build scalable, developer-facing libraries.
