What is a Software Engineer?

At Castlight, the role of a Software Engineer is pivotal to our mission of simplifying the healthcare journey. You are not just writing code; you are building the digital infrastructure that helps millions of users navigate complex benefits, find the right care, and manage healthcare costs. This position sits at the intersection of data-driven decision making and user-centric product development.

You will work on high-scale platforms that aggregate and analyze vast amounts of health data. Whether you are focused on backend services using Java and Spring Boot, frontend interfaces in Angular, or full-stack feature development, your contributions directly impact how users interact with the healthcare ecosystem. The work requires a balance of technical precision—given the sensitive nature of healthcare data—and creative problem-solving to deliver intuitive, seamless experiences.

Common Interview Questions

These questions are based on real interview experiences from candidates who interviewed at this company. You can practice answering them interactively on Dataford to better prepare for your interview.

Getting Ready for Your Interviews

Preparation for Castlight requires a blend of fundamental computer science knowledge and practical application development skills. The interview team looks for engineers who can not only solve algorithmic problems but also discuss the "why" and "how" behind their architectural choices.

You will be evaluated on the following key criteria:

Technical Proficiency & Fundamentals Your interviewer will assess your grasp of core computer science concepts, specifically Data Structures and Algorithms (DSA). While the difficulty is generally rated as "Medium," you must demonstrate clean coding practices and the ability to optimize for time and space complexity. Recent interviews have also placed significant emphasis on specific frameworks like Spring Boot and Angular, as well as database query writing.

System Design & Architecture For mid-to-senior roles, you will face questions regarding REST API design and system scalability. You need to show that you can design robust backend services that integrate well with frontend applications. Expect to discuss trade-offs, data modeling, and how you structure applications for maintainability.

Communication & Collaboration The Castlight interview style is often described as a "discussion." Interviewers value candidates who can articulate their thought process clearly. You will be evaluated on how you handle feedback, how you clarify ambiguous requirements, and your willingness to engage in a two-way dialogue rather than just delivering a monologue.

Culture Fit & Adaptability Castlight values diversity of thought and a user-first mindset. You will be assessed on your ability to work in a collaborative environment where cross-functional teamwork is essential. Be prepared to discuss past projects in depth, explaining your specific contributions and how you navigated challenges within a team.

Interview Process Overview

The interview process at Castlight is structured to evaluate both your technical depth and your cultural alignment. It typically begins with an initial screening, often with a recruiter, to verify your background and interest. This is followed by one or two technical phone or video screens. These rounds usually involve a mix of coding exercises via a shared editor and conceptual discussions about your past work.

If you pass the screening stage, you will move to the onsite (or virtual panel) loop. This stage is rigorous and can involve 3 to 5 separate rounds. You will meet with potential peers, hiring managers, and cross-functional partners (such as Product Managers). These sessions cover live coding, system design, and behavioral questions. The atmosphere is generally described as welcoming and professional, though the process can be lengthy depending on scheduling.

One distinctive aspect of the Castlight process is the emphasis on "discussion" over interrogation. Interviewers often frame questions as collaborative problems. However, candidates should be prepared for a process that requires patience; timelines can vary, and proactive communication is sometimes necessary to keep things moving.

This timeline illustrates the typical flow from application to offer. Note that the Technical Screen phase may involve multiple rounds (coding focus vs. project focus) before moving to the final panel. Use the time between rounds to review your fundamental concepts and practice explaining your past project decisions.

Deep Dive into Evaluation Areas

Based on candidate data, Castlight’s technical evaluation focuses heavily on practical coding skills, framework knowledge, and system design fundamentals.

Data Structures & Algorithms (DSA)

This is a core component of the screening and early onsite rounds. You are expected to write syntactically correct code and optimize your solutions.

Be ready to go over:

• Arrays and Strings – Manipulation, sliding windows, and two-pointer techniques.
• Graphs and Trees – Traversal algorithms (BFS/DFS) are frequently mentioned.
• Logic Puzzles – Game-based logic (e.g., designing a game board or solver) has appeared in past interviews.
• Hash Maps & Sets – Efficient data retrieval and storage.

Example questions or scenarios:

• "Implement the logic for a Minesweeper game, handling board generation and user clicks."
• "Traverse a graph to find the shortest path between two nodes."
• "Solve a medium-level array manipulation problem to find specific target values."

Frameworks & Practical Application

Unlike some companies that focus solely on LeetCode, Castlight often tests your knowledge of the tools you will actually use on the job.

Be ready to go over:

• Spring & Spring Boot – Dependency injection, annotations, and creating microservices.
• REST APIs – Designing endpoints, handling HTTP methods, and status codes.
• Frontend Frameworks – Questions on Angular logic and component lifecycle (for full-stack roles).
• Database Queries – Writing raw SQL queries or discussing ORM mapping.

Example questions or scenarios:

• "How would you design a REST API for a healthcare scheduling system?"
• "Explain the difference between specific Spring annotations and when to use them."
• "Write a SQL query to fetch patient records based on complex join criteria."

Behavioral & Project Experience

You will likely have a specific round dedicated to your past experience and behavioral responses, often with a Hiring Manager.

Be ready to go over:

• Project Deep Dives – Explaining the architecture of a previous project and your specific role in it.
• Conflict Resolution – How you handled a disagreement with a product manager or another engineer.
• Mentorship – How you support junior team members (for senior roles).