Krzysztof Ziolkowski
Senior Backend Engineer
Amsterdam, Netherlands
Senior backend engineer with 8+ years building and operating production systems in fintech and blockchain. Strongest in TypeScript, real-time pipelines, APIs, observability, and reliability under load.
Work Preferences
Salary
USD 120,000 – 150,000
Skills
Work Experience
Lead Platform / Payments Engineer
raster.finance
Aug 2025 — Mar 2026
Owned backend reliability for payment flows and core NestJS/TypeScript services, including on-call support and incident handling. Stabilized inherited services by adding guardrails (timeouts, retries, feature flags) and tightening operational runbooks. Implemented observability and alerting (logs/metrics/traces) to improve failure detection and speed up debugging in production. Made pragmatic architecture and implementation trade-offs to keep delivery moving while reducing production risk. Worked across infrastructure and databases to resolve latency, correctness, and availability issues in live payment workloads.
Backend / Solana Engineer
2137.dev
Jan 2025 — Present
Built low-latency indexing infrastructure for Solana DEX data across RPC and gRPC endpoints. Developed an algorithmic trading bot with sub-second decision and execution flow for latency-sensitive market conditions. Designed on-chain/off-chain coordination for trading workflows where transaction ordering and execution timing affected outcomes. Built real-time pipelines to ingest, normalize, and react to market events for automated execution.
Senior Scala Developer
SoftwareMill
Aug 2024 — Apr 2025
Built event-driven backend services with Kafka and Google Pub/Sub using the Typelevel stack (cats-effect, fs2). Designed and deployed Kubernetes microservices, including custom operators for automated resource management.
Founder / CTO
cryptom.app
Mar 2023 — Aug 2024
Shipped production Solana programs and supporting backend services; owned reliability and fixes after deployment. Built TypeScript backend services exposing REST APIs and WebSockets for on-chain workflows. Owned CI/CD pipelines, cloud deployment, monitoring, and incident resolution across Azure and GitHub Actions.
Senior Scala Developer
Vidua
Aug 2022 — Mar 2023
Developed and operated a security-sensitive e-sign platform using Scala and AWS (SSL/PKI-focused).
Scala Engineer
Valsea
Mar 2022 — Aug 2023
Implemented high-throughput Scala services using Akka for crypto-related systems.
Junior Scala Developer / Data Engineer
Scalac (Nordea)
Jun 2019 — Mar 2022
Built streaming data pipelines and ML-backed services for regulated financial and messaging platforms.