Lead Data Migration Engineer (.NET)

The Role You will lead the data migration workstream for a compliance-critical public-sector registry system. The core challenge: converting a fully normalised relational database into an event-sourced architecture, migrating large volumes of document files, and ensuring every data related decision is documented and approved by the client. This is not a standard backend role. You need to understand legacy data deeply, make domain-informed decisions under uncertainty, and deliver under tight timelines with high client visibility. IN SHORT: 🌍 Remote work or on-site (Wrocław, Bielsko-Biała) – your choice! 💰145 - 170 PLN/h + VAT ☑️ B2B contract Data Migration & Legacy Systems experience • Proven experience with large-scale data migration projects: ETL, transformation pipelines, cutover planning. • Hands-on experience with event sourcing (relational-to-event model transformation): decomposing relational data into domain events with deterministic ordering. • Experience with legacy database analysis: reverse-engineering un(der)documented schemas, understanding data semantics and relationships without complete documentation. • Experience with data quality handling: nulls, duplicates, inconsistent formats, missing fields, validation rules. • Familiarity with document/file migration at scale: metadata extraction, filename parsing, large-volume validation and dealing with corrupted or ambiguous data or metadata. Core Skills • Strong knowledge of backend design patterns (dependency injection, repository, mediator, factory). • English language skills (B2+ minimum): required for clear communication with stakeholders and documentation of architectural decisions. • Hands-on experience with CQRS, Domain-Driven Design, and Event Sourcing. • Ability to design and implement aggregates, entities, value objects, and bounded contexts. • Skilled in building systems that enforce clear separation of concerns, scalability, and maintainability. • Solid understanding of clean architecture principles. Technical Skills • Strong experience with .NET / C# backend development. • Practical knowledge of Modular Monolith. • Experience with PostgreSQL and modern ORM frameworks (e.g. Entity Framework or equivalent). • Experience with Marten DB or willingness to learn quickly. • Exposure to CosmosDB or similar NoSQL/document databases. • Experience designing and consuming RESTful APIs. • Docker: confident setup, troubleshooting, and local environment management. • Good exposure to cloud environments, ideally Azure infrastructure and services. • Comfortable working with SQL at an advanced level: complex queries, schema analysis, data profiling, and ad-hoc investigation of production data. Domain & Governance • Rapid domain understanding: ability to quickly absorb unfamiliar, regulated business domains (registries, compliance, legal records). • Governance mindset: documenting decisions, maintaining audit trails, getting formal client sign-off. • Experience working with subject matter experts to define and validate data transformations and mappings. • Public-sector, institutional or regulatory software experience is a significant advantage. Mindset & Working Style • Proactive problem solver: you find workarounds when blocked, explore alternatives, and escalate intelligently - you don’t stop and wait. • Autonomous: you structure your own work, identify next steps, and act without being prompted. You take ownership of your deliverables. • Curious about data: you enjoy investigating legacy systems. • Comfortable with ambiguity: you make progress when not everything is defined, and revisit decisions as understanding grows. • Pragmatic engineer who can balance domain purity with real-world business needs. • Strong stakeholder engagement: you proactively reach out to SMEs, business analysts, and client representatives, challenge assumptions, and drive clarity. • Clear communicator: you are able to explain architectural and domain modelling decisions to both technical and non-technical stakeholders. • Resilient and persistent under pressure: you are comfortable working with tight deadlines, high client expectations and compliance scrutiny. Reasons Why You Would Enjoy Working With Us • We work in the latest technologies and with international clients, and our projects are polished from < to /> - learn about some of the projects we have completed. • We organize TechTalks, meet-ups and create guilds where we exchange knowledge - you can learn a lot from your teammates. • We have a close-knit team and we make sure to have regular integrations - we often go out to celebrate together. • You can work remotely or choose to work from our offices in Wroclaw or Bielsko-Biala. However, we count on your openness to occasionally visit the office for team meetings or client visits, or possible occasional trips to the client's headquarters. • You can adjust your working hours to suit your needs, starting your day between 7:00 and 10:00 am. • You can work with great specialists in their fields who also have a sense of humor and other after-hours hobbies. It is the people who create the unique atmosphere and relaxed atmosphere at CSHARK. • We have a flat structure - we are not a corporation and don't want to be one 🙃. • We offer bonuses for employee referrals (from 3000 PLN to 7000 PLN). • We organize remote English classes and provide access to the company library. You can also become an author/author of articles published on our technical blog - https://cshark.com/blog/.