Cossack Labs is a British company, headquartered in London, with R&D offices across Ukraine. We support innovators by protecting innovations. Our data security solutions assist businesses of all sizes and industries protecting their sensitive data against external attackers, insider threats, mis-configurations while remaining compliant with regulations.
16 жовтня 2025 бронювання

Python full-stack developer (middle) (вакансія неактивна)

Київ, Львів, віддалено

This position is open exclusively to Ukrainian residents currently living in Ukraine (preferably in Kyiv or Lviv).

Our product team is looking for a full-stack Python developer with hands-on experience in building UI applications, ideally someone open to learning or already exploring Go or Rust. You’ll help create tools used by engineers worldwide and contribute to mission-critical projects. We’re primarily looking for mid-level specialists. However, if you’re more senior and have a background in cryptography, security, or systems programming, we’d be happy to talk.

Requirements:

  • Python 3, Django or aiohttp 3+ years
  • Asyncio, queues, synchronisation
  • Django ORM or Sqlalchemy Core
  • PostgreSQL, raw SQL
  • JavaScript, React 2+ years
  • HTML5 / CSS3
  • Docker, docker compose
  • Linux, bash
  • Understanding of GOF, SOLID, Dependency Injection, Clean Architecture principles, Modular Monoliths
  • Understanding of asynchronous and multi-threaded programming: asyncio, threading, multiprocessing
  • Good spoken and written English (B2+) for team communication and code documentation

Nice to have:

  • Golang
  • Typescript
  • OAuth2
  • Prometheus
  • UIkit
  • RabbitMQ
  • gRPC
  • Datatables (javascript)
  • GitHub Actions

Main responsibilities:

  • Take ownership of developing user-facing features with a focus on responsive and intuitive design
  • Build efficient and reusable front-end systems to power our web applications
  • Write clean, maintainable, and well-documented code
  • Participate in code reviews and contribute to both individual and team growth

What to expect from us:

  • We build applications for clients, write code for developers, and document how it all works — for both
  • Everyone on the team is happy to help, but we also respect each other’s time and know how to find answers ourselves
  • Tech writing isn’t our favourite task, but we do create solid technical documentation when needed, and we’re lucky to have a tech writer to help with that
  • We prefer doing things right the first time over patching things endlessly later
  • We value healthy perfectionism, a sense of beauty in engineering, and a good sense of humour

Hiring process:

  • Resume review — up to 5 business days
  • Test task — estimated time 3-4 hours
  • Introductory meeting with the Head of development & solution engineering
  • Technical interview with several team members
  • Offer discussion

What’s in it for you?

  • Competitive compensation with a flexible and clear bonus scheme
  • Paid vacation — 21 business days per calendar year
  • Paid sick leaves
  • Hybrid work model: this position allows for a combination of in-office and remote work as needed
  • Combining technologies: hardware engineering, software engineering, cryptography, information security
  • You will work with people deeply interested in security engineering, you will learn a lot
  • Reasonable time budgets and an attitude to build things well — we prioritise building for decades, rather than just until the next release
  • Conferences, books, courses — we encourage learning and sharing with the community. Our team members share a a lot in talks, workshops, and blog posts
  • Public track record in the open-source aspect of our products.

Our software is well-known amongst security-aware teams, recommended by OWASP, and popular for easily solving complicated security challenges. Apart from building “off-the-shelf” solutions, we design custom security solution for novel problems. We work in the B2B space, with customers such as power grid operators, payment processors, legal companies, and million-user customer applications. We cater to young ambitious startups and well-established enterprises, that use our software and solutions as a core part of their security arsenal.