Staff Software Engineer

What we are looking for:

• 7+ years of backend software engineering, with strong production Java experience — Spring Boot and ideally Kotlin too
• Deep, hands-on Apache Kafka knowledge: Streams, state stores, topology design, and operational behavior — not just produce/consume
• Experience building real-time, event-driven distributed systems in multi-tenant SaaS environments
• Solid database fluency: MongoDB, PostgreSQL, Redis — you know when to use what and why
• Hands-on AWS experience: EKS, Kinesis, S3; comfortable reading and writing Terraform and Helm
• Track record of taking ownership of a messy, under-documented domain and making it better
• Ability to work directly with product and business stakeholders — you can translate between engineering and everything else
• Clear written and verbal English; the team is international
• Based in or willing to relocate to Kraków, Poland

Nice to have:

• Experience with IoT or BLE telemetry systems
• Go or Python for tooling and automation
• Familiarity with AsyncAPI, Drools rules engine, or OAuth2/Keycloak
• Background in a high-growth Series B/C product company

The kind of Engineer we are hiring:

You should be comfortable with ambiguity, allergic to sloppiness, and capable of holding a high bar while still shipping. If you think AI tools are optional extras rather than a core part of how modern engineers work, this is not the right role.

Our team is the connective tissue of this platform. We own the full data ingress pipeline — from third-party devices (Cisco, Aruba, and beyond) to our internal Kafka backbone — and we own egress: streaming enriched location and telemetry data out to downstream systems, external APIs, and partner platforms. We are rebuilding this domain the right way: event-driven, observable, documented, and built to scale.

We need a technical anchor — someone senior enough to raise the bar, pragmatic enough to ship, and confident enough to drive alignment across engineering and product.

What you will work on:

Data ingress & device integration

Own the pipeline that brings external device data into the Kontakt.io platform. Build and maintain robust integrations with Cisco Spaces, Aruba, and similar third-party infrastructure. High-volume BLE telemetry, Kafka Streams, gRPC — multi-tenant SaaS where both correctness and latency matter.

Data egress & external integrations

Build and evolve the egress layer that streams enriched location and event data to partner systems and customer-facing APIs — real-time position feeds, alarm forwarding, standards-compliant adapters. You own how the outside world consumes Kontakt.io data.

Architecture & technical leadership

You will drive the architectural evolution: what to rewrite, what to stabilize, and how to sequence it without breaking production. You establish the engineering standards — documentation, testing with Testcontainers, observability with Prometheus/Grafana — and you hold the team to them.

Cross-team ownership

Work directly with product stakeholders to translate business requirements into engineering decisions. When scope is unclear, you clarify it. When dependencies block the team, you resolve them.

,[Design, build, and maintain Java/Spring and Kafka Streams-based services processing real-time BLE and IoT telemetry at scale, Own ingress integrations with third-party location platforms — from protocol understanding to production reliability, Build egress pipelines streaming location and event data to downstream systems via REST, gRPC, and WebSocket, Drive architectural decisions and document them — the team currently operates on verbal agreements; you will change that, Use AI tools as a core part of your development workflow: code generation, debugging, documentation, prototype acceleration, Define and enforce testing standards using Testcontainers and CI pipelines (Jenkins, GitHub Actions), Instrument services with Prometheus and Micrometer; build Grafana dashboards that give the team real operational visibility, Collaborate with Data Platform and SRE teams on Kafka topology, state store configuration, and infrastructure ownership, Mentor engineers on the team — through code reviews, design sessions, and honest feedback] Requirements: AWS, Kafka, Kubernetes, Claude Code, Terraform, Java, MongoDB, PostgreSQL, AWS S3, Spark Streaming, BLE, Keycloak, Kotlin Tools: Jira, Confluence, GitHub, Jenkins. Additionally: Sport subscription, Private healthcare, Flat structure, Small teams, International projects, Free coffee, Free parking, Bike parking, Shower, Free snacks, In-house hack days, No dress code.