Senior Backend Developer (freelance)

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Own and evolve the backend architecture for IoT projects: data ingestion pipelines, API design, infrastructure decisions
Make technical trade-off calls and defend them clearly to the team and to clients
Design and maintain cloud infrastructure on AWS (EKS, Aurora, DynamoDB, Timestream, S3) with production-grade reliability
Lead technical discussions: RFCs, architecture reviews, post-mortems, because you see the need, not because someone asked
Mentor other backend engineers, raise the bar on code quality, and set patterns others can follow
Work side by side with firmware engineers, mobile developers, QA, PMs, and clients
Use AI tools as part of your daily workflow, not as a party trick
Challenge product and technical assumptions when something doesn't add up, even when it means a harder conversation

90-180 PLN/h net B2B, depending on your experience
Truly flexible hours: you organize your day
Fully remote, with pet-friendly Warsaw office + Gdansk cowork if you want them
Access to our internal knowledge-sharing: tech talks, experiments, side projects
When the first 3 months work out, and that depends on the work, the project pipeline, and business timing, there's a real path to a permanent contract with a fixed monthly salary, 26 days paid leave, 10 sick days, Saltus medical care, and a training budget

7+ years of backend development, with a meaningful chunk spent leading technical direction, not just writing code
Strong Node.js skills in production systems at scale (not "I followed a tutorial once")
Deep, hands-on AWS expertise: EKS, Aurora, DynamoDB, Timestream, S3
Kubernetes (EKS), Docker, and Terraform: you've built and maintained real infrastructure, not just clicked through the console
Solid understanding of distributed systems, event-driven architectures, and data pipelines
Experience with MQTT or similar IoT messaging protocols
CI/CD pipelines you've designed yourself (GitHub Actions, GitLab CI, Jenkins)
English at B2+, written and spoken: you'll be in rooms with US-based clients and you need to hold your own
The ability to translate business needs into technical decisions and explain those decisions to non-technical stakeholders
Strong opinions, loosely held: you propose direction, you defend it, and you change your mind when the evidence says you should

Previous IoT or connected device projects, especially anything involving telemetry at scale
Golang in production (we're adding it alongside Node.js)
Observability stack experience: tracing, metrics, structured logging
Security mindset for cloud-connected devices: secrets, mTLS, OTA updates
Genuine curiosity about the devices your backend talks to, not just the cloud side of the story

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