Karos is building the first real alternative to public transport for short-distance trips, powered by smart daily carpooling.

Every day, thousands of passengers ride with Karos, and we partner with hundreds companies and local authorities, including our newest major win with Île-de-France Mobilités.

We’re looking for a Senior Backend Engineer to help us scale our mobility platform, tackle real engineering challenges, and shape the future of sustainable mobility in Europe.

Why you’ll love working with us:

- Real-world impact: Your work directly reduces CO₂ and improves daily mobility.

- Engineering depth: Real-time matching, geospatial logic, multi-tenant architecture, large-scale data, not a CRUD app.

- High autonomy within a small, senior, pragmatic team.

- Fast iteration with quality: Your features ship quickly, coordinated with product, grounded in proper analysis and built to last.

- Mission with purpose: Helping people move more affordably and sustainably.

What you will do:

-Build the backbone of our mobility platform

Design and ship backend features powering mobile and web products.

Keep our platform reliable and fast as we process millions of daily data points.

Contribute to refactoring and evolving a mature, high-traffic codebase.

-Solve juicy technical challenges

Real-time rider matching and routing

Geospatial processing at scale

Multi-tenant B2B architecture

Performance bottlenecks and optimization

Data and Payment reliability for finance, clients, and territories

Propose and drive architectural evolutions

-Build with a product mindset

Work closely with PMs and Designers to understand real user problems.

Turn ideas into impactful, measurable features.

Care as much about outcomes as about technical quality.

-Raise the bar within a senior team

Join a squad that values ownership, clarity, and simplicity.

Influence technical decisions and engineering culture.

No people management required, though growth toward tech leadership is possible.

🧪 Our stack

Python, Django/DRF

MySQL, BigQuery, Clickhouse

GCP, Docker, Terraform

Cloud Tasks, RabbitMQ

GitHub Actions, Sentry, Datadog

We stay pragmatic: pick the simplest tool that solves the problem well.

🧑‍🚀 What you bring

Significant experience (6+ years or equivalent depth) in backend engineering.

Strong command of Python and backend fundamentals.

Experience navigating & improving large, existing codebases.

Solid foundation in databases, performance, and scaling patterns.

Experience with cloud environments, CI/CD, and production deployments.

A product mindset and care for user impact.

Clear communication, ownership, and ability to articulate technical decisions

Ability to reason about existing services and long-term architectural trade-offs.

🎯 What success looks like after 3-6 months:

Delivered several impactful backend features, end-to-end.

Taken ownership of a domain in the backend platform.

Improved part of our architecture in performance, reliability, or clarity.

Become a trusted partner for product & design.

Contributed to raising engineering standards within the team.

💚 Why it’s exciting

Your code will be used daily by real people.

You’ll work on complex, meaningful engineering problems.

A culture that favors ownership over processes.

A mission that matters: making daily mobility greener and more accessible.

Hiring Process

A human and transparent process completed in 3 weeks

1. Intro Call - 60 min

Casual conversation with our CTO.

2. Technical Deep Dive + Case Study - 2h

Architecture & experience discussion with senior backend engineers.

May include a short, relevant, no-tricks technical exercise.

3. Product Conversation - 60 min

Meet our CPO to discuss product vision, priorities, and collaboration.

4. Final Conversation - 30 min

With the CTO: alignment, mission, long-term growth.

We value clarity and respect. You’ll get visibility at every step.