Dominik Krzemiński
Senior backend engineer / tech lead
Rzeszów, PL · Remote · me@krzemo.dev · krzemo.dev · github.com/krzemooo · linkedin.com/in/krzemooo

ABOUT

Senior .NET backend engineer and tech lead since 2017, focused on payment, identity and real-time platforms. Designs and runs distributed systems in production, from legacy takeovers to cloud-native microservices. Strong in security-minded design, third-party integrations and mentoring teams. Also builds MCP servers and LLM-facing APIs to automate delivery work.

EXPERIENCE

Senior Backend Engineer / Tech Lead — Enixware
Nov 2023 – Nov 2026 · Remote · Full-time
- Technical lead of a transactional marketplace platform for digital goods with card and crypto payments (.NET microservices, PostgreSQL, MongoDB, Redis, AWS ECS, Terraform): architecture, releases, incident response, security reviews and cloud spend, keeping the platform reliable and efficient under growth.
- Design and delivery, as the main contributor within the team, of the platform's core backend services (B2B crypto payout gateway, OAuth2/OIDC identity provider, real-time pricing engine, payments, KYC and anti-fraud flows), which removed entire classes of recurring production errors and made key customer journeys faster.
- Targeted improvements to infrastructure, observability and testing: significantly lower infrastructure costs, an end to noisy daily failures in authentication and payments, faster CI and integration tests; team mentoring through code reviews, trainings, .NET Aspire and OpenTelemetry adoption and an agent-driven delivery workflow.

Senior .NET Developer — BlueSoft
Aug 2023 – Oct 2023 · Remote · Contract
- Legacy takeover for a food-production and delivery company: the outdated system reverse-engineered from partial code drops and brought up locally, followed by a modernisation plan that simplified key user flows, improved onboarding and filled critical feature gaps.
- On-site work in the client's production facility: the end-to-end process walked through and staff from each department interviewed about pain points and expectations, then translated into a phased, lower-risk rollout and UX improvements aligned with how people actually work.

.NET Developer — mobitouch
Oct 2022 – Aug 2023 · Remote · Full-time
- Backend of an event-driven microservices e-learning platform for school students (ASP.NET Core, Clean Architecture, CQRS, RabbitMQ, gRPC, Azure, Kubernetes), from development through a successful go-live with a large initial user base to stable operation in production.
- Hybrid identity across a WordPress user base, the .NET services and Azure AD B2C; performance analysis together with the hosting vendor and the client's business team, which uncovered misconfigured Azure database options owned by a third party and led to fixes that improved reliability.
- First-line response to production incidents (including out-of-hours when needed), client meetings to plan changes and fixes, smaller outsourced .NET projects and onboarding support for new engineers.

.NET Developer — Ideo Software
Jun 2021 – Oct 2022 · Rzeszów, PL · Full-time
- Backend development of a regulated online-games platform (ASP.NET Core) as part of the delivery team: integration of an undocumented third-party game-engine API through a proxy layer with no vendor support, hardened so that erroneous user actions put minimal load on the external API.
- Tech lead and later the only backend engineer on the project: client and business meetings, scoping and pushing back on requests, release and deployment planning, support for the frontend team and all technically complex support tickets.
- Structured logging and tracing on Azure and removal of unnecessary dependencies from an outdated project template, which significantly improved performance and made it much faster for support to meet SLA and respond to users.

.NET Developer — MukiSolution
Nov 2017 – Jul 2021 · Rzeszów, PL · Contract
- Technical support for a hospitality booking-platform SaaS (.NET Framework, SOAP, SQL Server): Jira ticket triage, bug tracing in code, manual data fixes and code annotated with change notes for developers.
- Greenfield ERP for small and medium manufacturing companies (.NET Framework, WinForms, SQL Server) developed as a team, including an RFID-based working-time module for plant entry and exit that replaced paper flows with a transparent, fully electronic process.
- On-site user interviews and satisfaction reviews at the pilot customer's plant, turned into backlog and delivered changes that gave the client more order and visibility into day-to-day operations.


EDUCATION

- Engineer's degree (Inżynier), Computer Science — University of Information Technology and Management in Rzeszów, 2018 – 2022
- Technician diploma, Digital Graphic Processes — Ekonomik Rzeszów, 2013 – 2017

SKILLS

AI: Anthropic API, Claude Code, Model Context Protocol
Backend: .NET, .NET Framework, ASP.NET Core, OpenIddict, .NET Aspire, AWS SQS, Azure Service Bus, FastAPI, FastEndpoints, gRPC, Hangfire, MediatR, RabbitMQ, SignalR, YARP
Frontend: Astro, Flutter, Next.js, React
Infrastructure: AWS, Docker, Azure, Cloudflare, DigitalOcean, Kubernetes, Terraform
Data: EF Core, MongoDB, PostgreSQL, Redis, ClickHouse, OpenSearch, SQL Server, SQLite
Languages: C#, TypeScript, Python
Tooling: xUnit, GitHub Actions, Grafana, Home Assistant, OpenTelemetry, Playwright, Sentry, Testcontainers

KEY SYSTEMS DELIVERED

- B2B crypto payout gateway — Multi-provider routing across several blockchain networks and stablecoins, signed callbacks, per-client limits, distributed locks, TOTP two-factor authentication, client SDKs published to NuGet.
- OAuth2/OIDC identity provider — OpenIddict: authorization code with PKCE, client credentials, rolling refresh tokens, MFA, external and SSO logins; production token-store bloat that was causing daily errors resolved.
- Payments, KYC and anti-fraud — Payout channels with retries and idempotency, KYC integration modelled as a state machine, deposit limits for new accounts, chargeback processing; a deposit double-spend race found and fixed during an internal security review.
- Real-time pricing engine — Multi-source price aggregation with liquidity filters and median thresholds, anomaly and frozen-feed detection, short-term snapshots; MongoDB, PostgreSQL, Redis, Hangfire, YARP, .NET Aspire.
- AI delivery platform — Production MCP servers exposing domain tools to agents, an LLM code-review quality gate and a spec → implementation → review workflow with human sign-off (Anthropic API, Claude Code).

LANGUAGES

- PL: Native · EN: Fluent

https://krzemo.dev/cv/ · https://krzemo.dev/cv.pdf