Lunar Software Engineer interview questions & guide 2026

The following questions reflect the patterns observed in Lunar interviews. Use these to understand the focus areas of our hiring team, rather than as a rigid script for memorization.

Technical & Domain Expertise

These questions assess your ability to build robust, scalable systems and your familiarity with our core technology stack.

• What experience do you have building and maintaining microservices in Go?
• How do you leverage the benefits of functional programming for fault tolerance?

Preparation at Lunar should focus on demonstrating both your technical depth and your ability to navigate the unique constraints of the healthcare industry.

Role-related knowledge – You must demonstrate proficiency in functional programming and an aptitude for high-concurrency environments. Be prepared to discuss how you have used your technical skills to solve real-world problems, specifically regarding scalability and system reliability.

Problem-solving ability – We value first-principles thinking. When presented with a challenge, show how you break down complex, ambiguous problems into manageable, logical components. We care less about the "correct" answer and more about how you arrive at a sound, defensible solution.

Culture fit & Values – Lunar is a mission-driven organization. We look for individuals who are intellectually curious, possess sound judgment, and are genuinely excited about the impact of their work. Demonstrate your ability to collaborate effectively within a team and your resilience when navigating a fast-moving, high-performance environment.

The Lunar interview process is designed to be a transparent and collaborative experience. We prioritize getting to know you as a potential colleague, which is why much of the process involves direct interaction with the team you would be joining. The pace is generally fast, reflecting our culture, and the rigor is high, given the critical nature of the software we build.

You can expect a mix of technical deep-dives and behavioral conversations. In many cases, you will be asked to complete a coding challenge, which is designed to provide you with a realistic look at the type of work you will encounter on the job. Our goal is to ensure that both you and our team have enough information to make an informed decision about this partnership.

This timeline illustrates the progression from initial technical screening to the final stages of the interview loop. Candidates should use this to pace their study, ensuring they are prepared for both the technical coding components and the deep-dive discussions on system architecture and behavioral scenarios.

Technical Architecture

We evaluate your ability to design systems that are resilient, fault-tolerant, and capable of handling real-time data.

Be ready to go over:

• Fault tolerance – Strategies for ensuring systems remain operational during hardware or network failures.
• Concurrency – How to manage high-volume, real-time data streams effectively.

Your primary responsibility is to contribute to the development of a modern, cloud-native platform that powers hospital operations. You will be expected to tackle high-impact projects, such as designing access control systems for sensitive clinical data or creating integration engines that connect disparate medical hardware.

Collaboration is central to your daily work. You will work closely with other engineers to ship infrastructure that supports rolling deployments and real-time data synchronization. You will also participate in the continuous improvement of our development practices, ensuring that as we grow, our code remains robust and our workflows remain fast and intuitive.

A strong candidate for a Software Engineer position at Lunar combines deep technical expertise with a growth mindset.

• Must-have skills – A minimum of 6 to 10 years of professional software engineering experience, proficiency in both object-oriented and functional programming, and a demonstrated ability to tackle challenging, novel engineering problems.
• Nice-to-have skills – Experience with Elixir, Phoenix, or Erlang is highly valued. Additionally, a background in building 0-1 products or experience within the healthcare technology sector is a significant advantage.
• Soft skills – Exceptional communication, the ability to articulate complex technical trade-offs, and a collaborative spirit are non-negotiable for success in our team-oriented environment.

Q: How difficult are the interviews? A: The interviews are rigorous because we are tackling some of the most complex problems in the industry. However, they are also designed to be professional and collaborative, focusing on your problem-solving process rather than "gotcha" questions.

Q: How much time should I spend preparing? A: We recommend focusing your time on reviewing system design fundamentals and functional programming concepts. Because our process is practical, ensure you are comfortable writing clean, robust code in a language you are proficient in.

Q: What differentiates successful candidates? A: Successful candidates show a mix of deep technical fundamentals, a strong product sense, and a genuine passion for our mission. They are also able to articulate their thought process clearly when faced with ambiguous, novel challenges.

Q: Is the coding challenge representative of the actual work? A: Yes. We design our coding challenges to mirror the types of problems you would solve in your first six months at Lunar, ensuring you get a realistic view of the work.

• Articulate your trade-offs: In every technical discussion, explain why you chose a specific approach, including the pros and cons of your decision.
• Focus on the "Why": When discussing past projects, explain the business impact and the technical "why" behind your design choices.
• Be curious about healthcare: Showing an understanding of the complexities of clinical workflows can set you apart from other candidates.
• Communicate your process: We are interested in how you think. Talk through your approach while coding or designing systems to give your interviewer visibility into your reasoning.

The Software Engineer role at Lunar is an opportunity to redefine the infrastructure of modern healthcare. By focusing on your ability to design robust, scalable systems and demonstrating your passion for solving mission-critical problems, you will be well-positioned to succeed in our interview process. Remember that we are looking for engineers who can think deeply and act decisively.

You can explore additional interview insights, practice questions, and preparation resources on Dataford to further sharpen your approach. We encourage you to reflect on your past technical achievements and be prepared to discuss them with the same level of depth and passion that you would bring to our team.

The compensation data provided represents the current market range for this role. Candidates should interpret these figures as a broad guideline that reflects various levels of seniority, experience, and specific team requirements within the organization.