Senior Java Developer in Poland

Location: Poland 

🌍Who we are:

Adaptiq is a technology hub specializing in building, scaling, and supporting R&D teams for high-end, fast-growing product companies in a wide range of industries.

🧩About the Product:

Our client is a major online gaming operator building a next-generation transactional platform for user account management. This is a greenfield project designed to operate in a highly regulated, high-volume environment and support millions of concurrent users. The platform will process financial transactions in real time and must ensure high availability, sub-second performance, data integrity, security, and full auditability. One of the key engineering challenges is maintaining reliability and performance during extreme traffic spikes and peak events. 

🌟 About the Role:

As a Senior Java Engineer, you will design and build the core backend services of the PAM platform from the ground up. You will own features end-to-end, from technical design and implementation to automated testing, production monitoring, and release. You will work closely with Principal Engineers on architecture and technical decisions, contribute to RFCs, and deliver production-ready code. You will have a high level of autonomy and real influence over the platform’s design, while taking strong ownership of reliability, performance, and correctness in a critical financial system.

📈 Key Responsibilities:

• Design and build backend services in Java 17+ (Spring Boot or similar) for wallet transactions, ledger entries, payment orchestration, bonus mechanics, and account state management.
• Develop REST APIs and event-driven integrations using Kafka or similar technologies for player-facing frontends, operations tooling, and external partners.
• Ensure correctness and reliability through idempotent operations, clear transaction boundaries, explicit failure handling, and strong unit, integration, and contract testing.
• Embed regulatory requirements into the platform, including KYC/AML checks, responsible gaming controls, and audit trails.
• Ensure production readiness with metrics, structured logging, distributed tracing, alerting, and participation in on-call rotations.
• Contribute to technical design and RFCs, participate in code reviews, and mentor other engineers.
• Use AI-assisted development tools as part of the daily workflow, following platform standards for context and prompts.
• Support live migration from the existing third-party platform, including parity testing, data validation, and cutover coordination.

💻 Required Competence and Skills:

• 5+ years of backend engineering experience with strong hands-on expertise in Java 17+ and a modern framework such as Spring Boot.
• Proven experience building and operating high-integrity transactional systems such as payments, wallets, billing, banking, e-commerce, or gaming.
• Strong relational database expertise (PostgreSQL or equivalent), including schema design, ACID transactions, locking, and performance tuning.
• Experience with event-driven architecture and messaging (Kafka, RabbitMQ, or similar), including idempotency and retry mechanisms.
• Strong testing practices, including automated unit, integration, and contract tests as part of the standard development process.
• Hands-on production experience with containers, CI/CD pipelines, monitoring/telemetry, and production incident troubleshooting.
• Solid understanding of multi-threading, system architecture, and fault-tolerant design patterns.
• Good written and spoken English, with experience working effectively in distributed.

➕ Nice to Have:

• Experience in iGaming, sports betting, fintech, or another regulated, high-transaction-volume domain.
• Exposure to Kubernetes and AWS, including VPC, IAM, EKS, and auto-scaling.
• Experience with compliance-driven development, including KYC/AML, responsible gaming, and audit requirements.
• Experience with AI coding assistants and agentic development workflows.
• Polish and/or Spanish language skills.

🚀 Why Us:

- We provide 20 days of vacation leave per calendar year (plus official national holidays of a country you are based in).

- We provide full accounting and legal support in all countries we operate.

- We utilize a fully remote work model with a powerful workstation and co-working space in case you need it.