Java Tech Lead (with React)

Our client is an international financial technology company building solutions that support transaction communication, balances visibility, reporting, and integrations across multiple banking systems.We are looking for a Backend Tech Lead to join a strategic rewrite of a core platform module. The role combines technical leadership with hands-on backend development, helping redesign a legacy component into a modern, scalable architecture.You will work closely with product stakeholders, platform engineers, and frontend teams to design and implement reliable, high-performance backend services that integrate multiple enterprise systems.IN SHORT:🌍 Remote work or on-site (Wrocław, Bielsko-Biała) – your choice!💰170 - 190 PLN/h + VAT☑️ B2B contractYour Daily MissionsLead the design and development of backend services for a core platform rewrite.Design scalable services responsible for transactions, balances, statements, and reporting data.Define API contracts and integration patterns between backend services, frontend applications, and external enterprise systems.Make key decisions around data modeling, search/indexing strategies, and performance optimization for million-row datasets with complex filtering, sorting, and pagination.Support frontend teams by ensuring API-first design and smooth integration with React applications.Ensure engineering quality through code reviews, architecture discussions, and mentoring other developers.Collaborate closely with product, frontend, and platform teams to deliver robust, production-ready systems.The Essentials We're Seeking7+ years of experience in backend or fullstack software development.Strong expertise in Java and Spring Boot, including designing modular backend services and REST APIs.Experience acting as a Tech Lead or technical owner responsible for architectural decisions.Solid experience designing scalable APIs and distributed systems.Strong understanding of data modeling in relational databases (e.g., PostgreSQL) and designing efficient query patterns.Practical experience with Elasticsearch (or similar search/indexing technologies) for filtering, search, and aggregation over large datasets.Experience designing hybrid data architectures combining multiple data sources.Experience working with external system integrations, including REST or GraphQL APIs.Familiarity with containerized environments (Docker, Kubernetes) and modern CI/CD pipelines.Understanding of security patterns in enterprise systems (OAuth2, OIDC, authentication and authorization flows).Working knowledge of React and TypeScript, enabling effective collaboration with frontend teams.Proven ability to break down complex architectural changes into manageable development phases.Experience using AI-assisted development tools (e.g., Cursor, Claude Code, or similar agentic coding tools) and openness to experimenting with AI-driven approaches to improve development efficiency and engineering workflows.Ability to combine hands-on engineering with technical leadership and mentoring.Nice-to-HavesExperience in FinTech, banking, or enterprise integration platforms.Experience with large-scale transactional or reporting systems.Experience with GraphQL integrations.Experience with data migration or legacy system modernization.Experience designing API-first platforms.Familiarity with observability practices (logging, metrics, tracing).Understanding of database partitioning and query optimization patterns.Reasons Why You Would Enjoy Working With UsWe 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/.