To help you target your preparation, we have broken down the primary technical areas where Photon candidates are evaluated.
Enterprise Backend Development
If you are interviewing for a backend or full-stack role, your expertise in building scalable, enterprise-grade APIs will be thoroughly tested. Interviewers want to see that you understand how to write secure, highly performant backend code that integrates seamlessly with modern databases and messaging queues.
Be ready to go over:
- Spring Framework & Spring Boot – Deep understanding of dependency injection, auto-configuration, Spring Security, and Spring Data.
- Microservices Patterns – API gateways, service discovery, circuit breakers, and distributed tracing.
- Database Optimization – Query tuning, indexing strategies, caching mechanisms (e.g., Redis), and managing connection pools.
- Advanced concepts (less common) – Asynchronous messaging with Kafka or RabbitMQ, reactive programming with Spring WebFlux, and containerization with Docker and Kubernetes.
Example questions or scenarios:
- "How would you design a distributed transaction system across three independent microservices?"
- "Walk me through how you would diagnose and resolve a database deadlock in a high-traffic Spring Boot application."
Frontend & UI Engineering
For frontend, UI, or full-stack positions, the evaluation focuses heavily on your mastery of modern JavaScript, responsive web design, and framework-specific architectures (such as Angular or Vue.js).
Be ready to go over:
- Core JavaScript/TypeScript – Closures, event loop, asynchronous programming, promises, and prototyping.
- State Management – Managing complex application state using tools like NgRx, Vuex, or Redux.
- Component Architecture – Designing reusable, modular, and highly performant UI components.
- Advanced concepts (less common) – Server-side rendering (SSR), progressive web apps (PWAs), micro-frontends, and custom Webpack or Vite configurations.
Example questions or scenarios:
- "Given a Vue.js repository with a performance bottleneck, identify why unnecessary re-renders are occurring and refactor the component state."
- "Explain how you would implement a secure token-based authentication flow on the frontend, ensuring protection against XSS and CSRF attacks."
Practical Problem Solving & Live Debugging
Photon places a high premium on practical, hands-on engineering. Many rounds go beyond theoretical questions to test your ability to read, understand, and debug existing codebases in real-time.
Be ready to go over:
- Algorithm & Data Structure Fundamentals – Arrays, strings, trees, graphs, and sorting/searching algorithms.
- Code Debugging – Navigating a pre-built project repository, identifying logical or configuration bugs, and fixing them.
- Code Quality & Testing – Writing clean, self-documenting code and accompanying it with robust unit tests (using JUnit, Mockito, Jest, etc.).
Example questions or scenarios:
- "Review this poorly written Java class, identify three major architectural or performance flaws, and refactor it live."
- "Solve this medium-difficulty algorithmic challenge on HackerRank within 45 minutes, ensuring your solution handles all edge cases."