Senior Software Engineer (front-end)

This role is suitable for a Senior front-end software engineer with at least four years of JavaScript development experience and a strong background in Angular, React, Vue.js, or a similar framework.

The candidate should be skilled in HTML5, CSS3, responsive design, Git, complex UI development, data structures, algorithms, and preferably REST APIs, front-end testing, C#/.NET, financial software, data grids, or data visualization.

They should be familiar with owning the full product lifecycle, translating wireframes and client requirements into scalable interfaces, collaborating with product and engineering teams, solving complex financial or mathematical problems, and communicating clearly with technical and non-technical stakeholders.

1. How would you structure a complex front-end application using React, Angular, or Vue.js?

I would separate the application into reusable presentation components, feature modules, shared services, and a clear state-management layer where needed. I would also establish consistent conventions for routing, API communication, validation, error handling, and testing to keep the codebase scalable.

2. How do you design a high-performance data grid for large financial datasets?

I would use virtualization, server-side pagination or filtering, memoized rendering, and carefully controlled state updates to avoid rendering unnecessary rows and cells. I would also measure performance with browser profiling tools and ensure sorting, formatting, and updates remain predictable for users.

3. How would you consume and integrate a RESTful API in a front-end application?

I would encapsulate API calls in dedicated services, define typed request and response models, and handle loading, retry, validation, and error states consistently. Authentication, cancellation of obsolete requests, caching, and clear user feedback would also be considered.

4. What techniques do you use to build responsive and precise user interfaces from wireframes?

I start by identifying the layout structure, reusable design patterns, breakpoints, typography, spacing, and interaction states in the designs. I then implement semantic HTML, flexible CSS layouts, and component-level styling while validating the result across browsers, screen sizes, and accessibility requirements.

5. How would you test a front-end component using Jest or a similar framework?

I would test observable behavior rather than implementation details, including rendering, user interactions, validation, loading states, error handling, and API-related outcomes. I would mock external dependencies where appropriate and combine unit tests with integration or end-to-end tests for critical workflows.

6. How would you optimize a JavaScript application with complex calculations and frequent data updates?

I would profile first, then reduce unnecessary work through memoization, efficient data structures, debouncing, batching, and selective component updates. Expensive calculations could be moved to Web Workers or the backend when appropriate, while maintaining accurate and traceable results.

7. How would you visualize financial data while preserving accuracy and usability?

I would define the meaning, units, precision, time zones, and rounding rules before selecting an appropriate chart or visualization. The interface should provide clear labels, tooltips, filtering, accessible alternatives, and consistent handling of missing, delayed, or invalid data.

8. What is your approach to state management in a mission-critical front-end application?

I distinguish local UI state from shared domain state and server state, keeping each as close as possible to the components that own it. Shared state should have explicit actions, predictable updates, normalized data where useful, and clear rules for synchronization and error recovery.

9. How do you maintain code quality and collaborate effectively using Git?

I use small, focused branches and commits, meaningful messages, pull requests, automated checks, and peer reviews. I also keep changes easy to validate, resolve conflicts carefully, and use CI to enforce formatting, linting, testing, and build standards.

10. How would you approach developing a feature that must work in both a cloud SaaS platform and an on-premises deployment?

I would identify deployment-specific constraints early, isolate environment configuration, and avoid embedding cloud assumptions in shared application logic. I would also verify API compatibility, security, performance, upgrade paths, and test the feature in representative environments before release.

Leversys is a growing capital-markets FinTech building leading convertible-bonds trading, risk-management, data, and SaaS platforms for global investment banks and hedge funds. As a Senior Front-end Software Engineer, you’ll own features across the full product lifecycle, transforming client needs and designs into precise, scalable interfaces while collaborating with experienced engineers and contributing to cloud and on-premises products. The stack includes JavaScript, Angular/React/Vue, HTML5, CSS3, responsive design, Git, REST APIs, and optionally C#/.NET and Jest. This is a full-time hybrid role in Belgrade, offering top-of-market salary based on experience, 25 days’ holiday, development support, and the chance to make a visible impact in a specialised, fast-growing financial technology company.