Senior Backend Engineer (Kotlin/Java)

Quick Facts

• Senior individual contributor Backend Engineer (Kotlin-first)
• Remote in Poland; occasional meetings in Poznań
• On-call: part of the backend rotation
• Stack: Kotlin, Spring Boot, jOOQ, PostgreSQL, Arrow, Google Cloud; also Codex/Claude Code

Description

You’ll join a long-running, single-deployable Kotlin service that acts as the merchant of record, handling payments, refunds, payouts, sales tax/VAT, manufacturing, shipping, and a public API with webhooks. The work emphasizes reliability for money-moving workflows, including idempotency and reconciliation, plus feature delivery with schema rollouts and safe production break handling via feature switches. You’ll direct development using coding agents, review their output, and own what gets merged.

Responsibilities

• Build product features end-to-end: database/schema changes, rollout strategy, and deletion of old paths after launch
• Ensure safe releases with feature flags and production observability
• Handle production incidents: disable features, coordinate with support, assess impact, fix, and reconcile
• Integrate and evolve partner/payment/tax/manufacturing/shipping integrations through stable APIs and failure handling
• Work with coding agents by reviewing outputs, running checks, and improving agent skills/hooks when mistakes repeat

Requirements

• Kotlin or Java on a Spring backend in production
• Strong SQL fundamentals (know what SQL runs and what ORM/abstractions hide)
• Correct error handling approach using return types (Either/Result/sealed types) vs exceptions
• Integrated at least one third-party API end to end (contract, retries, idempotency, failure modes)
• For HTTP calls or background jobs: explain cost, performance impact, and how failures occur
• Shipped at least one feature with measurable impact on users or revenue
• Provide an example of a request you did not build as asked, including what you did instead and why
• Completed a task outside your usual area (e.g., data pull, Terraform module, partner sandbox) and explain how you ramped up
• Clear written English

Benefits

• PLN 22,500–38,000 net/month on B2B, long-term (range depends on end-to-end impact and shipped bets)
• 26 days off per year at full monthly fee
• MacBook; private healthcare with dental; sports card; English lessons; educational budget; accounting support
• Equity in a US-based company