Senior or Mid Backend Software Engineer (m/f/d)

Tech stack you’ll work with

(If you haven’t touched every tool yet, no worries — we’ll get you up to speed.)

Your mission and responsibilities

Mid Backend Software Engineer

• Implement new micro-services and extend existing ones in Go.
• Help groom user-story requirements and surface performance / scaling concerns early.
• Write unit, integration and API tests; review PRs.
• Tune data-models in DynamoDB & Postgres for low-latency, high-throughput workloads.
• Pair with DevOps on CI/CD and observability improvements.
• Participate in on-call rotation as we’re building high available fintech system

Additional tasks of the Senior

• Design and drive high-scale, low-latency services (tens of thousands of orders / sec).
• Lead architecture reviews, challenge assumptions and keep tech debt in check.
• Partner with Product on roadmap feasibility & effort sizing.
• Be a mentor to less experienced colleagues

Your qualifications and experience

• 3+ years of professional back-end experience (ideally 1 year+ in Go).
• Solid grasp of cloud-native design (RESTful APIs, event-driven patterns).
• Working SQL and NoSQL skills; know when each shines.
• Comfort diagnosing performance bottlenecks in distributed systems.
• Ability to work on-site in Warsaw twice a week (Tue & Thu) and remotely otherwise.

Nice to have

• Exposure to serverless architectures on AWS.
• Experience with Kafka or another high-volume message bus.
• Knowledge of automated trading, market data, or FIX/crypto exchanges.
• Familiarity with Infrastructure-as-Code (Terraform or CDK).

Contract

B2J / Employment contract

Location

Hybrid (Warsaw – in-office every Tuesday & Thursday)

Why us?

What We Offer:

• An experienced, welcoming team that loves clean, well-tested code.
• Real impact: the features you ship go straight into production for live traders.
• Flexible hours, modern tooling, and a fintech domain that’s never boring.
• Occasional work travel to Germany (Munich / Berlin)
• 20 days PTO on B2J
• Multisport card