Software Engineer (Mobile & Sensing)

Cartesian is building spatial intelligence for indoor environments to drive operational efficiency. We’re tackling one of the biggest challenges in the $35T global retail industry: in-store inventory visibility. Our platform delivers accurate indoor positioning and actionable product location insights, helping retailers streamline operations, optimize workflows, and reduce inefficiencies. Leveraging wireless signals, we provide a uniquely scalable, infrastructure-free solution already deployed by international fashion brands.

Founded by an MIT engineering professor and alum behind the award-winning, patented core technologies, Cartesian spun out in 2023. Originally backed by the prestigious SBIR Award from the US National Science Foundation, we've bootstrapped to a live product that's now deployed in over a dozen countries and have been aggressively scaling in the market.

Our first product is the only indoor inventory positioning system that operates on existing handheld devices. Mobile provides the critical interface between users and our system: you will build both SDKs and end-user apps that collect high rates of data from on-devices and peripheral sensors, provide real-time feedback and help users spatially locate items in stores.

We’re actively adding new customers and expanding our product portfolio, so our work spans the full lifecycle of development, from early scrappy prototypes of a whole new app to thoroughly-tested production systems. Importantly, we work extensively with peripheral hardware - connecting to RFID scanners, barcode readers, and third-party integrations. Thus, our mobile applications need to seamlessly integrate with, connect to, and stream data from a wide array of hardware.

Our team is still small, and there’s no dedicated PM assigning out tickets. Engineers are expected to closely collaborate with all aspects of the business to figure out what needs to get done, pull in the right people for prioritization and sign-off, and move projects forward autonomously.

The team works in-person 5 days a week by default, right in Kendall Square next to MIT and the Charles River.

Engineers succeed at Cartesian not based on what they know, but how they approach problems, learn what they don’t know, and continuously make the product, team, and company better. Our interview process aims to assess the engineering principles and judgment (why and how) that you’ve refined through experience, rather than the experience itself.

We look for the following traits:

• High Growth: You’re intrinsically curious. You have a track record of learning hard things quickly. You actively seek critical feedback from others. You work on things that matter, even if they are unfamiliar. You’re defined by where you’re going, not where you started.
• High Ownership: You have high expectations for yourself and others, and never settle for mediocrity. You deliver outcomes not tickets. You know that the last 10% of work takes 90% of the effort, and still get it done on-time. You care about the system as a whole: making things easier for the next person, and fixing problems rather than waiting for others to do so.
• Low Ego: You don’t know everything. You want the best ideas to win. Nothing is below you. You are a good leader, listener and mentor.
• Engineering Excellence: You default to simple, maintainable solutions. You are intentional with your decisions and balance technical quality, business priorities, and long-term maintainability. You know that aligning on why and what is much more important than the how. You communicate well in English, not just Kotlin.

For the mobile role in particular, you should be deeply passionate about mobile development, diving deep into why things work a certain way (e.g. the data from this output doesn’t look correct), focusing on simplicity, and building seamless interactions for users.

• We are looking for slope, not experience. That said, this is not an entry level position and to be competitive, we expect 2+ years of experience building mobile products at a company with a high engineering bar.
• Passion for building applications in the physical world - connecting sensors, data, insights and people together via performant, intuitive interfaces.
• Track record of driving complex, end-to-end projects.
• Strong opinions on how to structure mobile applications for correctness, maintainability, and performance.
• Excellent written communication (designing projects, sharing progress updates, reviewing other people’s work, getting buy-in on decisions, etc.)

• Comfortable contributing to the backend when needed.
• Experience shipping and maintaining mobile SDKs to enterprise customers at scale.
• Experience defining, implementing, and automating testing on real-world hardware.

We’re a fast-moving MIT startup at an important inflection point for our product growth and direction. We are building a talent-dense team of engineers and applied researchers to solve hard, high-impact problems in retail operations.

You will have outsized ownership and autonomy. You will grow extremely quickly and make important contributions to our product, engineering culture, and company direction. We will push you to become a better engineer, and we will expect the same from you. 

• Mobile: Android, Kotlin
• Hardware: RFID & Barcode Readers (e.g. Zebra)
• Backend: FastAPI, Python, Hatchet
• Infrastructure: Azure, Kubernetes, Helm, Terraform
• Data: Postgres, Blob Storage, Parquet
• Machine Learning: PyTorch, Ray
• Frontend: Next.js, Typescript, Tailwind

The typical interview process takes 2-3 weeks from start to finish. We can move more quickly for candidates who might have a short timeline or competing offers.

1. Screen (20 minutes)
2. Behavioral Interview with Isaac (Co-Founder) (30 minutes): We front-load this conversation, as it is the best predictor of long-term fit, and we’d rather find that out early for both sides.
3. Three Technical Interviews (45-90 minutes each): 
1. Project Deep-Dive: Tell us about a recent project you worked on. We want to know the messy details and walk away learning something new.
2. Coding Exercise (Live): Based on a simplified, but realistic task. The live aspect helps us understand your approach and allows you to ask questions.
3. System Design: How would you design a complex, multi-part feature?
4. References
5. Offer!

$120,000 - $180,000 annually + equity