100ms Software Engineer interview questions & guide 2026

The following questions reflect patterns observed in recent interview cycles. While the specific problems may change, the focus on foundational computer science and system architecture remains consistent. Use these to gauge the depth of your preparation.

Data Structures and Algorithms

These questions test your ability to write clean, efficient code under pressure. Focus on edge cases and time complexity.

• Trapping rainwater problem.
• Problems involving binary search.

Preparation should focus on bridging the gap between theoretical knowledge and practical application. Do not rely on rote memorization; instead, practice articulating your thought process aloud as you solve problems.

Role-related knowledge – You must have hands-on experience with the programming languages and frameworks relevant to the stack. Interviewers look for deep understanding rather than surface-level familiarity, especially regarding performance bottlenecks.

Problem-solving ability – This is evaluated through how you structure your approach to a problem before you start coding. Demonstrate your ability to break down complex requirements into smaller, manageable components.

Leadership and Communication – You will be evaluated on your ability to explain your design decisions and respond to feedback during the interview. Being able to justify your choices—and acknowledge potential trade-offs—is a sign of a senior-level mindset.

The interview process at 100ms is designed to be rigorous but collaborative. You can generally expect a combination of technical screens, deep-dive coding assessments, and system design discussions. The process often begins with an initial conversation to gauge your background, followed by one or more rounds focused on Data Structures and Algorithms (DSA). If you progress, you will likely face a mix of low-level design (LLD) and high-level system design, sometimes involving a take-home project that tests your ability to understand the 100ms product.

The philosophy here is to assess your practical engineering instincts. Interviewers are often looking for the "how" and "why" behind your code, rather than just the final output. The process can be fast-paced, and you should be prepared to discuss your past work in detail, including the hurdles you faced and the solutions you implemented.

This timeline illustrates the progression from initial screenings to technical deep-dives. Candidates should use this as a roadmap to manage their preparation energy, ensuring they are polished on coding fundamentals early on and ready to discuss architectural trade-offs in later rounds. Note that the inclusion of a take-home project or "semi-system design" round can vary based on the specific team's needs.

Technical Rigor

This area assesses your core engineering competence. Strong candidates don't just solve the problem; they write readable, maintainable code and consider performance implications.

Be ready to go over:

• Algorithmic efficiency – Understanding Big O notation and choosing the right data structure for the task.
• Code quality – Writing clean, modular code that handles edge cases effectively.

As a Software Engineer at 100ms, you will be responsible for maintaining the high standards of our real-time infrastructure. Your day-to-day work will involve collaborating with product managers and other engineers to translate high-level requirements into scalable technical solutions. You will be expected to own your code from design through to deployment, which includes debugging production issues and optimizing existing services for better performance.

You will often work in an agile, fast-moving environment. The ability to switch between deep technical focus—such as optimizing a database query or reducing latency in a streaming pipeline—and broader architectural discussions is essential. Success in this role means contributing to a team that values technical excellence, speed of execution, and a user-first perspective.

A strong candidate for this position brings a combination of solid foundational knowledge and a track record of building reliable software.

• Must-have skills – Proficient in at least one modern programming language, strong grasp of data structures and algorithms, and experience with distributed system concepts.
• Nice-to-have skills – Prior experience with video streaming technologies, WebRTC, or high-concurrency infrastructure.
• Experience level – Demonstrated ability to deliver complex features in a production environment, typically supported by 2+ years of relevant engineering experience.

Q: How much time should I dedicate to preparing for the technical rounds? A: Dedicate at least 2–3 weeks of focused practice on algorithmic problems and system design fundamentals, especially if you haven't interviewed in a while.

Q: What is the most common reason candidates fail the technical rounds? A: Lack of clarity in communication. Interviewers want to see your thought process; if you code in silence, you miss the opportunity to show your problem-solving logic.

Q: Is the take-home project mandatory? A: Depending on the specific role and team, a take-home assignment may be required to assess your ability to navigate a larger codebase and understand the 100ms ecosystem.

Q: How should I prepare for the culture fit or managerial rounds? A: Reflect on your past projects and be prepared to discuss specific instances where you handled conflict, met tight deadlines, or took ownership of a difficult technical problem.

• Think Aloud: Always verbalize your thought process. Even if your initial approach has a flaw, the interviewer wants to see how you identify and correct it.
• Ask Clarifying Questions: Never jump straight into coding. Ask about constraints, scale, and specific requirements to show you are thinking about the business impact.
• Know Your Resume: Be prepared to dive deep into any project you list. If you mention it, you should be able to explain the technical decisions behind it.
• Research the Product: Understand what 100ms does. Being able to relate your technical solutions to the challenges of real-time video will set you apart.

A Software Engineer role at 100ms offers the unique opportunity to build technology that defines how the world connects in real-time. By focusing on your core technical fundamentals, sharpening your system design skills, and clearly communicating your problem-solving process, you will be well-positioned to succeed. Remember that interviewers are looking for your potential to grow and contribute to a high-performing team.

Candidates can explore additional interview insights, practice questions, and preparation resources on Dataford. Stay focused, remain curious, and approach each round as a collaborative discussion. Your preparation will pay off—go into your interviews with confidence.

The compensation data provided covers typical ranges for this role, including base salary and potential equity components. Candidates should interpret these figures as market benchmarks, keeping in mind that total compensation packages are often adjusted based on experience level, specific team placement, and location.