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
✨Join Local Tech Meetups
Get out there and mingle with fellow developers by joining local tech meetups. It’s a fantastic way to meet people who might be working at techstack Recruitment or know someone who does. Plus, you can pick up some trendy tech skills and trends while you're at it!
✨Contribute to Open Source Projects
Show off your coding chops by jumping into open-source projects. Not only does this give you practical experience, but it also gets you noticed in the dev community. You'll create a killer portfolio that speaks volumes about your skills to techstack Recruitment.
✨Tap into Online Developer Communities
Don’t underestimate the power of online developer communities like GitHub, Stack Overflow, and even Reddit. Participate in discussions, share your projects, and build your visibility. We can often find opportunities through these channels that can lead to a full-time gig at companies like techstack Recruitment.
✨Explore Job Boards Specifically for Tech Roles
Keep your eyes peeled on job boards that focus on tech roles. Sites like TechCareers or Stack Overflow Jobs can often have listings for companies like techstack Recruitment that might not show up on broader job sites. Make it a habit to check these regularly, and don’t hesitate to apply directly through our website!
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 coding skills:When applying for a software engineering role, it's super important to showcase your coding skills. Make sure your CV includes your tech stack, any relevant programming languages you’re comfortable with, and examples of projects you've worked on. If you have a GitHub profile, link it up! We love to see code in action.
Tailor your portfolio:For a full-time role, we’d expect to see some solid examples of your work in your portfolio. Make sure to include at least two or three projects that highlight your problem-solving skills and your ability to work with different technologies. Focus on the projects that are most relevant to the position at techstack Recruitment.
Craft a killer cover letter:Your cover letter is your chance to stand out—make it personal! Explain why you want to work at techstack Recruitment and how your skills align with the role. Show us your passion for software development. We dig enthusiastic candidates who understand the value of collaboration and continuous learning!
Be clear and concise:When it comes to writing your CV and cover letter, clarity is key. Avoid jargon that could confuse us and stick to simple, direct language. Highlight your achievements with quantifiable results where possible, and keep everything easy to read. A well-organised application goes a long way!
How to prepare for a job interview at techstack Recruitment
✨Brush Up on Your Coding Skills
For a full-time software engineering role, it's crucial that we stay sharp with our coding abilities. Expect technical questions that might involve solving problems on the spot or discussing algorithms. Practise on platforms like LeetCode or HackerRank to get comfortable with the types of questions that often come up.
✨Know Your Tools and Frameworks
Make sure we’re well-acquainted with the tools and technologies listed in the job description. Familiarise ourselves with any specific frameworks or programming languages mentioned. If techstack Recruitment uses React or Node.js, for instance, be ready to discuss how we’ve used them in previous projects or coursework.
✨Showcase Your Projects
Bring along a portfolio that highlights our best work. This could be code samples, GitHub repositories, or any side projects we’ve built. Make sure we can talk through our thought process for each project, especially the challenges we faced and how we solved them—this shows our problem-solving skills in action.
✨Prepare for Behavioural Questions
While technical skills are key, full-time positions also require cultural fit. Be ready to discuss our previous experiences and how we handle teamwork, conflict, and deadlines. Brush up on the STAR method—Situation, Task, Action, Result—to clearly articulate our past experiences when discussing how we've contributed to a team.
